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Diagnostic Scan Reading

chevyjunky77

chevyjunky77

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Does anyone know the correct readings/indications for the individual points in a diagnostic scan? I have found a few individual items amongst the threads. Did I miss an all important thread somewhere?

'88 Jimmy 5.7L. Low, rough, slight surging at park idle. Driving is "chugging" as if missing on a number of cylinders. Was throwing a 32 code (EGR SW) Here is what I got.

119162126_744085629771099_1969401288940877429_n.jpg

119200800_795683474593447_6810621778530368116_n.jpg

119162477_911244122730873_516186349386088189_n.jpg
 
your 02 cross counts are 0, a good o2s will be around 30-50. This could be old 02 sensor, leaking exhaust, vacuum leak, computer not commanding fuel mixture. O2 reading is close to 14.7 to 1 ratio, what is your elevation?
Map voltage is good for idle.
other than the cross counts and the low eng temp, Block learn Mode (BLM) is highish put might be from the eng temp.

How old is your secondary ignition? cap rotor wires plugs? The egr could have dirt in it, causing a slight vac leak at idle, will have less influence at speed so doubt it is causing the chugging. Maybe fuel delivery there. (pump)
 
Wes,

The O2 Cross Counts makes sense. The O2(mV) reading is the static voltage the ECU sends to the sensor. Elevation is 29ft. Exhaust is brand new. 180deg Tstat so not too far from operating temp.

Does <20 BLM points make a drastic change considering 128 is normal? INT number is near perfect.

Cap, plugs, and wires all new. Triple checked. Timing checked. New tank, filter, and sending unit (pump).
 
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A little history... Vehicle was having issues with acceleration above 50mph. Under 50mph ran well with a slight shudder/miss. Kickdown at WOT is lacking. Slight surging at idle (200-250 rpm). Overall high idle.

Rebuilt TBI. Front vacuum ports seriously restricted. Overall condition probably the worst I have seen. Mechanically sound.

After rebuild idle issue is resolved. All other symptoms remained. Vehicle now stumbles from full stop through 40mph. "Chugging" while driving has now manifested itself.

After a couple days "chugging" and shudder increased significantly. No CEL. Hooked up scanner and found CODE 32 "EGR SW FAULT". I am assuming a bulb was removed at some point. Reset codes. Symptoms returned to previous condition until code tripped. The EGR was in fact bad. Replaced and code has not returned. Driving performance slightly better.

Could the carbon build-up in the TBI "tricked" the ECU from requiring the EGR to operate?

Just for fun I dropped out of OD. "Chugging" and shuddering very light throughout driving range. Beginning to wonder if I have multiple problems. A torque converter or lock-up issue?
 
I'm still thinking fuel, new regulator? good spray from injectors ? re-torque the intake and tbi.
 
TBI should have a 195 tstat so 164 is cool, should be slightly rich.
 
@Wes Harden

Retorque was also done. Spray pattern from injectors looks good.

I can confirm that when the TCC Lockup and TCC Solenoid are engaged the truck runs like arse. Even more so once it goes into OD.

O2 voltage is all over the place. Still no Crosscnts. I am going to change the sensor.
 
Replaced the O2. As you can see it has already improved numbers. I dont understand why it wont record the Cross Counts but I can watch them fluctuate while live. Overall it is better. However, when going into TCC Lockup and Solenoid activation it still shudders. Was able to get it to kickdown this time. That may change the next drive, who knows.

119250276_2743686675952468_645595952832810082_n.jpg
 
What rpm is the lock up happening.
Hmm all suspect area's seem covered.
It's going to end up being something simple maybe a poor connection somewhere, bad ground.
 
I did an IAC reset. Afterwards the reading trickled down to 65. At idle the thing is the best it has ever sounded.

The lockup happens at 45 after it hits 3rd. OD kicks in at 50. After driving in OD for about thirty seconds at 55 I punched it. It kicked down in passing gear and picked up speed, quite lethargic to say the least. After coming out of passing gear and transitioning back into OD it shudders worse than ever. Let off the fuel and ease back in it returns to its norm. Right now this is the only issue left.

Wes Harden said:
It's going to end up being something simple maybe a poor connection somewhere, bad ground.
Click to expand...
I am starting to believe this myself.
 
Try disabling lock up in third, I can lock mine up in 2nd and 3rd manually, If I let it up shift I get shudder for a second.
4th should shift in around 42-45 with lockup. I don't remember factory 3rd lock up in 88. Do you have big tires and factory gear ratio?
 
Wes Harden said:
Try disabling lock up in third, I can lock mine up in 2nd and 3rd manually, If I let it up shift I get shudder for a second.
4th should shift in around 42-45 with lockup. I don't remember factory 3rd lock up in 88. Do you have big tires and factory gear ratio?
Click to expand...

33s on factory ratio. RPO says 3.43

Sorry misspoke earlier. 45 is 4th and 50 is the O/D. Truck runs good when O/D is disabled. The issue with the transmission (assumed) just recently started and what brought me to looking at all the other settings. Has been for the better as I have learned a lot of small things that have greatly increased my knowledge base.
 
Ok so at 50 mph in od you are turning 1250 rpm, in 3rd at 1 to 1 a little better 1773 rpm to do 50 mph. 65 mph is 2300 rpm in 3rd.
your motor isn't making any power at 1250 rpm. You want 4.56 at minimum 4.10. 4.56 in od at 65 mph is 2143 perfect cruise rpm.
 
Thanks for all the info @Wes Harden. I will have to go in and check the actual gear ratio as the RPO is not always correct. I did notice the RPO sticker has an order number. Not sure if that is normal for a stock build as my 80 and 77 do not have that note. I prefer 3.73 or 3.92 it seems to be the perfect all around gear for me. I have run that gear on up to 40s with no power issues.

I tried a product that guarantees to eliminate trans shudder. It worked like a charm. The Jimmy rolls out like it just came off the floor. Pretty confident it is a last ditch effort before it dies.
 
Your trans issue sure sounds like the engine RPM is too low for the load, but now that you mentioned the PROM, is there a stock chip in your ECM or has someone maybe changed it? As I read through this, I was thinking that may be the issue, now that you're telling me the PROM isn't listed, I'm really wondering. The TCC lockup can be set with the PROM, and I've seen all kinds of crazy stuff done like using a Camaro PROM, homemade ones that just don't have certain settings, using the wrong ECM for the vehicle, using the wrong PROM for the ECM, etc. While you'd be having other issues if it was something serious, you may want to check that chip!
 
anwat said:
Your trans issue sure sounds like the engine RPM is too low for the load, but now that you mentioned the PROM, is there a stock chip in your ECM or has someone maybe changed it? As I read through this, I was thinking that may be the issue, now that you're telling me the PROM isn't listed, I'm really wondering. The TCC lockup can be set with the PROM, and I've seen all kinds of crazy stuff done like using a Camaro PROM, homemade ones that just don't have certain settings, using the wrong ECM for the vehicle, using the wrong PROM for the ECM, etc. While you'd be having other issues if it was something serious, you may want to check that chip!
Click to expand...

The thing that gets me is there was no Engine RPM issue prior to me doing a "reset". What I mean by that is starting fresh when it comes to a maintenance schedule. For instance brakes, differential fluid change etc etc. I drove it frequently for two weeks beforehand to get a good idea of what should be a priority.

What is a "normal" PROM code for the vehicle?
 
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