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Rough running and dieing

greengiant0311

greengiant0311

1/2 ton status
Joined
Jan 19, 2007
Posts
243
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Location
Camp Warner
Hello all. I have been chasing some gremlins and need some help. Replaced the MAP sensor and fuel filter in my 88 burb. It still keeps dieing, there's spark but still keeps sputtering out. Im racking my brain here and getting ready to blow it in place. Please help, Thank you.
 
Don't throw any more parts at it. Have you checked fuel pressure?

Are you getting any codes? Does the check engine light work properly?
 
It was throwing a 33 code which is MAP sensor. Ive used the OBD 1 reader since replacing the sensor and its showing no codes besides the 1 2 code. Fuel pressure seems good, I haven't checked it. But with it being so sporadic its hard to get it to a shop. Im trying to do as much work as I can to it but it gets frustrating sometimes.
 
There are a LOT of things that can cause issues, just some more likely than others. You can check timing, but altitude shouldn't affect it to the extent you mention.

Autozone loans a fuel pressure checker for free, it's fairly quick and easy to test (I do it at the fuel filter, way easier to access than further forward) and at least you could rule that out for free.

Don't know your skill level, but if there is a timing issue, you know the proper procedure to set base timing, correct?

Is this a problem that just started happening? Not real likely it's a timing issue if it just randomly started, as long as your distributor is still more than hand tight.
 
It is a problem that just started but have had different issue prior. Kinda roigh idle occasionally then surging on occasion. Not sure what to do. Probably wont make it to zone or OReilly to test is an issue as well.
 
It is very, no, extremely common for fuel pressure to be low due to a split hose in the fuel tank thanks to ethanol. Not worth dropping the tank just to check, if you have ANY way of getting a pressure tester. I don't know when the fuel hose in the tanks started being ethanol resistant, but I had mine fail and it was dated 1995. Someone may have replaced it before you and you'd be wasting time and money dropping the tank for something that's already been corrected.

If you look here: http://www.gmwbody.com/forum/faq/gm-obd-1-trouble-code-information/?wap2 you'll see what actually sets the codes. Since your code 33 is gone, and you get only code 12 now, the ECM is thinking everything is kosher. Have you done a test for vacuum leaks? Throttle body base gasket (and throttle shaft bore if high mileage) are sources for a vacuum leak. Not likely with no code, however if it's running bad enough, it may not set a code due to everything else being out of whack.

Realistically the very first step should be a thorough inspection of the underhood area, to include plugs, wires, cap, rotor, vacuum lines (to include leaks at gaskets, etc), wires and connectors, etc. Once you've gotten that part down, you should move onto the more in-depth stuff like fuel pressure, etc.

Can you reach under the EGR and move the valve freely with the engine off? Wouldn't seem a probable issue with a slowly sputtering out engine, but it's another check to do. Just because it moves freely doesn't mean it's working properly, but it's free and easy to do.
 
Are you checking it with the EST bypass disconnected? What does the core support sticker say? IIRC 4* was the highest "base" (again, EST bypassed) timing for any of the TBI trucks.
 
Close enough IMO. A degree or two is not likely to make a difference. Since it's running bad, keep everything "stock" as best you can, at least until you find the problem. Running too much initial leads to detonation, you can't afford to add that to your existing problem.
 
Set it to 0 with EST bypass unplugged. Turn truck off. Plug bypass back in. Start truck. Clear any codes that might be stored (sometimes setting base timing sets a code). Done.

Of course, this is assuming the core support sticker says 0* base. You set it to whatever the sticker says. Again, 1 or 2* off isn't going to be noticeable. This isn't the source of your problem unless probably 6*+ retarded.
 
Well I ended up not adjusting the timing. Figured it wasnt that far off. Reset the codes and it starts and is runnung fine. Gonna replace the temperature sensor, heard that could be an issue, tricking ecu to think truck is running cold. Any thoughts?
 
Reference post 2.

There are no moving parts in a CTS. They fail, but not commonly. I really, really suggest getting a scantool if you are going to keep the truck. You can physically see the temperature the ECM thinks the engine is, which you can reference against your actual temp gauge. Parts=money, tools=money.
 
Ok so I bought the innova 3120. Its showing 10 codes, 42,35,33,32,31,55,54,52,51,43. A couple of those are MAP sensor which I have replaced already and some say its a PCM issue. I'm lost in the sauce on this, should I reset or replace the PCM any help is appreciated.
 
I just went through a timing issue with my Jimmy. The distributor was loose. This caused a number of issues. The worst part was, it was loose enough that the timing was actually changing from day to day as I drove it. The truck seemed hard to start sometimes. Then it had a rough idle. Then it would start fine and run fine. Then it would be crappy again the next day. By the time I got it fixed it was pinging under acceleration! Long story I know, but it was confusing to diagnose because some of the symptoms changed daily. You mentioned checking the timing twice with two different results. It could be possible. Check the distributor closely. Make sure its tight and make sure the contacts are clean and corrosion free. Also, could you have bad fuel? Or a fuel filter that needs to be replaced? Ethanol has a tendency to absorb water and definately has a much shorter shelf life than non ethanol fuel. Hope you figure something out!!
 
Holy crap that is a load of malfunctions! You sure it's set/working properly? You said only a code 12 from the ECM, the scanner will show the same code(s) as the check engine light, something isn't adding up.
 
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