Dismiss Notice

Welcome To CK5!

Registering is free and easy! Hope to see you on the forums soon.

Score a FREE t-shirt and membership sticker when you sign up for a Premium Membership and choose the recurring plan.

I need some Fuel Injection advice!! 87 up folks!!!!

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Grim-Reaper, Mar 30, 2001.

  1. Grim-Reaper

    Grim-Reaper 3/4 ton status Author

    Joined:
    Feb 17, 2000
    Posts:
    7,385
    Likes Received:
    0
    Location:
    Atlanta
    Well I got an e-mail from Lady Reaper yesterday afternoon and it said "The 79 has to go". It's too difficult for her to deal wit the infant seat loading it in and out of the back seat where the only belt is that will hold it correctly. She want's something with 4 doors (preferably a car she say's but let her look at what I found and see).
    Well the little car lot down the street has a 3/4 ton 87 sub on it. Went and looked at it. SUPER nice body and interrior. Little wear on the carpet and driverseat but for a 87 it is better than average. Loaded even has working dual A/C. Freash paint and other than a light scratch from a bush or something it look almost new from the outside. Even has new tires. My guess with the way it's optioned is this was a retired couples pull truck and it appears to have been impecably maintained.

    On to the problem I did find. Something not right with the FI. Beat a confession out of the sales man. Truck has something unplugged on the ECU. It stalls at traffic lights if the ECU is plugged in. Sounding like either a clogged EGR, O2 problem and they got the thing running in Limp mode. Had a miss that the guy swears was not there the day before and it smells like it's running rich. While I'm good with Quads and have a good general knowledge of FI and how it works I have not messed with GM TBI before so looking for advice and hopefully a worst case dollar figure if you have seen this problem before.

    Has an exhaust leak that almost sounds like cracked manifold but that's no big deal I have some of those laying around if 85 mainfolds will work on the 87 motor. I did notice that it has the center bolt valve covers. Does that mean it's a Vortec? Didn't think they went to that till 89.
    Thanks in advanced.

    Diging it in the dirt with my K5's
    Grim-Reaper
    <A target="_blank" HREF=http://grimsk5s.coloradok5.com/>http://grimsk5s.coloradok5.com/</A>
     
  2. mattman

    mattman 1/2 ton status

    Joined:
    Feb 15, 2001
    Posts:
    152
    Likes Received:
    0
    Location:
    Austin, Texas
    Can't say for sure on the EFI problem. I got and still can't figure my problems out but onto your head question. In '87, GM redesigned the 350. Changed heads to centerbolt (not Vortec heads, believe those came out in '95?) and one piece rear main seal. I think in limp mode the engine runs on the MAP sensor and throttle position sensor, can't remember about speed sensor. Could be bad VSS sensor or possibly vacuum problem. I know if you disconnect the MAP sensor hose with it running it will die. Hope this helps some.
     
  3. WhiteWhomper

    WhiteWhomper 1/2 ton status

    Joined:
    Sep 23, 2000
    Posts:
    227
    Likes Received:
    0
    Location:
    Highlands Ranch, CO.
    Well, as for the centerbolt valve covers, '87 was the first year for these but they are not Vortec. Vortec did not appear until '93 The main difference with these heads vs earlier heads is that the center intake bolts go in straight up and down and not at an angle like previous heads. Meaning you can't use that old Quadrajet manifold in the garage without mods. Plus, the '87 or may have been '86 and up motors use the one piece rear main seals. I have the same stalling problems with my '87 every once in a while, (but usually starts right back up) and I am still trying to locate the actual cause. Hurry and get the answer so I can try to fix it with mine.
     
  4. Emmettology 101

    Emmettology 101 3/4 ton status

    Joined:
    May 9, 2000
    Posts:
    8,126
    Likes Received:
    0
    Location:
    FL
    When you plug the ECU in, is it throwing the check engine light on? If so, then get the codes and see what the ECU is telling you.....



    Mike [​IMG]
    See <font color=green>EMMETT</font color=green> -&gt; <A target="_blank" HREF=http://emmett.coloradok5.com>http://emmett.coloradok5.com</A>

    "Pimpin aint easy!"
     
  5. fr8train

    fr8train 1/2 ton status

    Joined:
    Aug 2, 2000
    Posts:
    1,712
    Likes Received:
    0
    Location:
    Maryland
    Well we cant really diagnose till the guy reconnects the wires that are to the ecm. You can semi fix a ghetto riging for a little while then it'll come up and haunt you. I had my ECM go up on my 88 Jimmy and caused all kinds of problems including what you have listed. If the ECM were connected right I would look into the Throtle Postion sensor then the EGR and O2. If this little sob is funny you can have erratic idle, stalling, etc... all kinds of annoying crud[​IMG].

    [​IMG]
     
  6. fr8train

    fr8train 1/2 ton status

    Joined:
    Aug 2, 2000
    Posts:
    1,712
    Likes Received:
    0
    Location:
    Maryland
    Dooh, just re-read your post. Check TPS then see if any of the harness wires have been screwed up to the ECM.

    [​IMG]
     
  7. Grim-Reaper

    Grim-Reaper 3/4 ton status Author

    Joined:
    Feb 17, 2000
    Posts:
    7,385
    Likes Received:
    0
    Location:
    Atlanta
    Well according to the guy at the lot. When the ECU is plugged back it it will run fine with no check engine light. Come to a stop and bam it stalls. Starts back up no problem but he seemed to indicate it never throws a light so unless it's a softcode that the ECU is storing there may be no code.
    EGR makes sence to me is it's sticking open when comming to a stop it can stall the engine. That truck is old enough the EGR position is not read by the ECU so it would not trip a code. TPS makes sence also.
    What costs are we looking at for the following.
    ECU
    EGR
    TPS
    O2
    Or any other probable parts I might have to replace.
    Thanks


    Diging it in the dirt with my K5's
    Grim-Reaper
    <A target="_blank" HREF=http://grimsk5s.coloradok5.com/>http://grimsk5s.coloradok5.com/</A>
     
  8. fr8train

    fr8train 1/2 ton status

    Joined:
    Aug 2, 2000
    Posts:
    1,712
    Likes Received:
    0
    Location:
    Maryland
    Tps for Napa cost me 54.95 in 2000
    Egr from them cost me 35.99 in 2000
    These were O.E. parts according to them. And the came in little delco boxes.

    The stuff you can get from Trashauto or PepGirls will be a lot cheaper. Though its isnt delco. It hasnt failed any of my friends yet.

    Jamie payed 215.99 for her computer of the 88 K5. Had to turn in the old one though as a core. This was at Autozone 2001.

    [​IMG] Dont steal my truck..I dont need anymore worthless junk over my fireplace.
     
  9. Kyle89K5

    Kyle89K5 1/2 ton status

    Joined:
    Feb 17, 2000
    Posts:
    2,273
    Likes Received:
    0
    Location:
    OKLAHOMA
    Computer will prb. be about $150
    O2 sensor, $25
    EGR Valve $50
    TPS $20

    At least thats the prices I was paying when mine was going funky. Might be a fuel delivery problem. A rebuild kit for the TBI won't run you much and you can do em in about 30 min. Sounds like a good deal.

    Your best bet might be to just take it to a shop that can hook a computer up to it. Not the little paperclip code reader things but an honest to god computer. It'll give you plenty of info.

    Just my lousy $0.02

    Kyle
    89K5
     
  10. HarryH3

    HarryH3 1 ton status Author

    Joined:
    May 31, 2000
    Posts:
    10,384
    Likes Received:
    2
    Location:
    Georgetown, TX
    The sales droid is feeding you a line of crap. If you unplug the engine computer, then the engine won't run at all. All the wiring goes into the computer in a couple of large connectors, so you can't just unplug a couple of wires. You need to find out exactly what they really have unplugged. Make sure that you see the "check engine" light come on when you first start the engine. They could have yanked the bulb if they coudn't get it to turn off. [​IMG]

    A bad throttle position sensor (TPS), manifold absolute pressure sensor (MAP), idle air control (IAC) motor, or even a leaking EGR valve or other vacuum leak can cause the engine to stall at idle.

    If you're seious about wanting to buy the truck, I'd suggest spending $50-100 to have it checked over by a mechanic. Could save you hundreds or thousands in the long run if he finds something major wrong with it that you overlooked.

    <font color=black>HarryH3 - '75 K5</font color=black>
    <A target="_blank" HREF=http://ThunderTruck.ColoradoK5.com>http://ThunderTruck.ColoradoK5.com</A>
     
  11. Brian 89KBlazer

    Brian 89KBlazer 1/2 ton status

    Joined:
    Feb 17, 2000
    Posts:
    779
    Likes Received:
    0
    Location:
    Ontario, Canada
    One thing about the EGR is that if it's going, then the truck will start to idle like a drag car with a lopey cam. Mine did just before the EGR cracked off from the rust!
     
  12. Blazer1970

    Blazer1970 1/2 ton status

    Joined:
    Feb 17, 2000
    Posts:
    1,600
    Likes Received:
    0
    Location:
    Old Mission, MI
    Coolant Temperature Sensor (CTS) could also cause the rich idle. I agree that it is best to try to get it hooked up to a computer where you can see the actual readings that the computer is getting from the sensors. Saves a lot of trial and error. The used car dealer should agree to this.

    Tim

    70 Blazer CST 4X4 350 SM465 NP205
    87 Burb 4X4 350
    01 GMC 2500HD 4X4 Duramax/Allison
     
  13. CaptCrunch

    CaptCrunch 1/2 ton status

    Joined:
    Feb 2, 2001
    Posts:
    3,596
    Likes Received:
    1
    Location:
    Minnesota
    Something is very fishy here grim... You can't unplug the ECM like someone else stated because that acts as the power distribution for the entire vehicle. All the things listed can cause problems, but if there is no check engine light then most of the sensors should be ok, but don't quote me on that. I'd check for a vac leak... and something else would be the TCC... try driving it slow not letting it get out of 2nd gear... does it stay running? Also I'd take it to a local mechanic and have him hook up a Scanner to it and drive around so he can watch the sensor readings... You can also check to see what cylinder is missing by using a PLASTIC pliers to pull plug wires till the idle doesn't change. Then test out the hole and see if it is dead. Another thing is if you think the computer is bad try a tap test... tap on the comptuer and see if it acts up... tap... nothing then tap a bit harder... but just one or two fingers.

    [​IMG]
    1987 Chevy K5 Blazer- 350 TBI
     
  14. Grim-Reaper

    Grim-Reaper 3/4 ton status Author

    Joined:
    Feb 17, 2000
    Posts:
    7,385
    Likes Received:
    0
    Location:
    Atlanta
    Capt
    Yes and no. Yes when the ECU has what ever is unplugged it does show a check engine light. Why it still runs is that's a early version of the FI and it is in Limp mode right now. No closed loop working (O2). Probably getting horrible millage and fouling plugs but it will run.
    It is such a early version that a lot of the diagnostics that we are use to it does not have. It does not read things like EGR It does not real time the temp sensors etc. Not even sure that version is tied into the HEI system like the newer models.
    The biggest reason for my Post was to get some idea what I need to repair if I get serious about this truck. It looks awsome but he is way high on the price concidering the miles and the run problem I need him to come down a good bit. I need hard data and I'm betting this guy knows whats wrong and what it will take to fix. I need to know also so I have leverage on the price. I have already found a simular one for far less that this one but haven't seen it so there may be a reason it's so low.

    Diging it in the dirt with my K5's
    Grim-Reaper
    <A target="_blank" HREF=http://grimsk5s.coloradok5.com/>http://grimsk5s.coloradok5.com/</A>
     
  15. HarryH3

    HarryH3 1 ton status Author

    Joined:
    May 31, 2000
    Posts:
    10,384
    Likes Received:
    2
    Location:
    Georgetown, TX
    Whatever he's unplugging, it isn't the engine control computer. That's tucked away behind the glove box. And since it reads all the sensors and provides the signals to power the injectors, the engine will not start with it unplugged. The 87's have a fair amount of intelligence built into them. They do control both the fuel and ignition from the computer. The distributor has no advance mechanism. The timing is all controlled by the amount of delay that the computer adds to the ignition circuit.

    The more I think about it, the more I think he's unplugging the circuit for the knock sensor and timing control. It's a small, black, flat module under the hood that's perhaps 3 or 4 inches square. That will definitely set the check engine light and kick the computer into limp home mode. Is this what he's unplugging?

    <font color=black>HarryH3 - '75 K5</font color=black>
    <A target="_blank" HREF=http://ThunderTruck.ColoradoK5.com>http://ThunderTruck.ColoradoK5.com</A>
     
  16. Thunder

    Thunder 3/4 ton status

    Joined:
    Jul 20, 2000
    Posts:
    8,946
    Likes Received:
    1
    Location:
    Northeast Nevada
    You really need to put a code scanner on it to find out what's wrong. If it is running as bad as you say something should come up. The only thing i have found that will sometimes not leave a trouble code is the O2 sensor. A bad O2 sensor will also make the truck run in bypass mode(limp mode)
    If the ECM is unpluged the truck will not run so he is unplugging something else.

    <P ID="edit"><FONT SIZE=-1>Edited by Thunder on 03/30/01 05:35 PM (server time).</FONT></P>
     
  17. jarheadk5

    jarheadk5 1/2 ton status

    Joined:
    Mar 6, 2000
    Posts:
    4,389
    Likes Received:
    0
    Location:
    PA
    Not sure what the difference is, but my 87 with TBI 305 has an EGR valve; just behind the TBI on the pass. side of the intake manifold. There's no wiring hooked up to it.

    It sounds like, among other things, the minimum air may need to be set.

    From experience, I can tell you that when the ECM shifts to Limp-Home, the Service Engine light comes on.

    Sounds to me like this deal might be too much trouble for Lady Reaper's daily driver...

    [​IMG] Semper Maintenance!
     
  18. Twiz

    Twiz 1/2 ton status

    Joined:
    Mar 8, 2001
    Posts:
    3,729
    Likes Received:
    0
    Location:
    Clearfield Ut.
    Grimm, to a salesman "unpluged the ECM" means someting was unpluged, mabe not the ecm, but something was unpluged. Sounds like a T.T.C. (Torque Converter Clutch) thing to me, like the Cap said. Think about it; if the sub. runs w/-something- unpluged, but stalls at stop lights when it is pluged in. What sounds logical? How does it run w/it pluged/unpluged at a idle? (if it changes it might not be a TTC, guessin on that- "limp" home mode might have an affect?) What sensors/switches are being used at the time when it stalls? (the TTC is not suposed to be engaged w/the brakes appied, but if everything else seems to be OK every where else, than that would eliminate those as a possible cause- did that make sence?) Sorry I don't have the sure fire fix, 87s are before my time (statred life in 93, with the new camaros)
    As far as leverage, (unless this is a fix-it, sell it place), this guy -might- not know anything about cars, just knows how to sell 'em. You have the leverage, you can walk at any time! This guy NEEDS to sell this car, and I'll bet he'll go way down if you let him know that you can and will walk off and the stalling thing buggs you(but don't be a jerk about it!) Forget about that "I got another guy looking at it too" bit. If he does, so be it. There are alot of fish in this pond! GOOD LUCK!

    Tiztid


    <P ID="edit"><FONT SIZE=-1>Edited by Twiztid on 03/30/01 11:40 PM (server time).</FONT></P>
     
  19. Gandolf

    Gandolf 1/2 ton status

    Joined:
    Aug 8, 2000
    Posts:
    764
    Likes Received:
    0
    Location:
    SF Bay Area
    Here's my .02. Because it starts right up after stalling, I think the stalling problem may be caused by a bad ignition module. (found in HEI ignitions) Starting right back up is a classic symptom of a failing ignition module. Two more symptoms are, no stalling until it's warmed up, and the stalling happens at random times. I don't know what the module will cost for a Chevy but the one for my 280ZX was $65. (Same stalling/EZ restart symptom)
    The running rich problem is probably the result of it's running in limp mode because they unplugged something. So find out exactly what they unplugged (it's not the computer), and plug it back in to see what happens. This might reveal another problem or with the ignition module replaced, it might run just fine. Good Luck.

    I missed your second post where you said it runs fine when plugged back in. Take it for a test drive with the engine stone cold. If it doesn't stall until warmed up, that's two out of 3 ignition module symptoms.

    '89 K5 Silverado..."You can’t have a real adventure, unless the outcome is truly uncertain".<P ID="edit"><FONT SIZE=-1>Edited by Gandolf on 03/30/01 10:10 PM (server time).</FONT></P>
     
  20. Pure Insanity

    Pure Insanity 1/2 ton status

    Joined:
    Mar 17, 2001
    Posts:
    4,579
    Likes Received:
    0
    Location:
    Dade City, Florida
    center bolt heads started in 86.same as 1pc rear main.vortec heads started in 96 or 97 i think 97tho( dont remember)centerbolt heads have the 2 center bolts canted up,&a higher rail around the cover(mucho less leaks)as for the TBI im glad ive got an 86.dont know squat about em.BTW86 up heads WILL accept an early intake,you just modify the 2 center holes.done it a few times.stick in a drill&twist to change the angle.then groove out a land for the bolt to seat in.or mostly seat in anyway. the vortec heads are a totally different animal,they only have 4 bolts per head to intake.2 front 2 back and none in the center.the 4 they have are vertical.way different angle.they take a different int.and thick int.gaskets,i think.120 if i remember right.you CAN drill the heads to accept 85 down int.or someplace sells em that way(dont remember who offhand)

    PURE INSANITY
    86 blazer silverado 400 horse 350 w/vortec heads 38 x15.5 swampers (40 hawgs next)10 bolts(blah)w/4:88s coming soon,14 bolt.
     

Share This Page