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Tech / General EngineIs your car making a strange sound or won't start? Thinking of adding power with a new combination? Need other technical information or engine specific advice? Don't see another board for your problem? Post it here!
Soo... my friend bought a 1988 gta 5.7 auto with 60,000 miles that had been setting for a while. Someone had worked on it before he got it, he got a mechanic to work on it but the guy jumped ship and hasn't been seen for months. He asked me if i would look at it. When i got it the distributor and maf were no where to be found. He bought a new distributor and maf. I put them in and timed it to 6 degrees. Idle bounces around with code 22 (tps low voltage). I loosed the tps bolts and the highest setting i can get from the tps at idle is .451 and code 22 goes away but its definitely not even close to the .54 setting ive read it should be. Battery voltage reading 12 volts. Switched tps sensor and had the exact same readings. I got a spare ecm from a friend so i swamped it but same results. Any ideas guys... im stumped. Im gonna replace plugs and wires since my friend already bought them but i have doubts as to if thats gonna help. Im not even sure if its got the correct prom in it. Its challenging trying to clean another persons mess up.lol If you have any ideas I appreciate it.
The TPS switch should be set to spec with the key on, engine off. If you can not get it set to specs with the key on, engine off, that switch is bad.
Thanks for the feedback. There was a new tps switch in the box located in the trunk. I guess one of the previous mechanics had purchased it. I did have the key on engine off when checking voltage. Both of the tps switches reflected the same exact numbers. I also checked the battery voltage and it was fully charged. I'll buy another switch and try it.
OK, one thing I failed to mention is that if the throttle body is dirty and has a build up of crud that's holding the throttle open even a tiny bit, it will effect the voltage reading while setting the TPS switch.
OK, one thing I failed to mention is that if the throttle body is dirty and has a build up of crud that's holding the throttle open even a tiny bit, it will effect the voltage reading while setting the TPS switch.
I couldn't wait. I just went to garage and cleaned throttle body then reset tps switch. It didn't help... same readings. .451 is as high as it will go. Another weird thing is the passenger fan never goes off. It runs all the time.
Service engine light came back on though. Code 36 this time so I'll research that code on this forum. Also rich lean flag coming on but when i rev the engine it goes off. Comes back on when rpms drop back down. Fumes from this car would choke a horse.
Can you unscrew tps sensor and plug the connector to it and manually with your finger move the clip, can you set it past 0.4v you getting?
Just removed and removed and tested... switch appears to be working fine. I was able to take out the lower bolt and turn the tps switch enough to get the correct setting. I think both of the tps switches I have are good since they are both showing identical readings when adjusting the switch. The idle air screw factory cap is still in place so I hate to remove it to adjust that... but I guess I may have too at some point. I'm gonna put the stuff the owner purchased (cap, wires, plugs) and confirm firing order then check it all again.
I cleaned, made sure length of valve was just under 1 1/8" and reset the IAC valve so that is one more thing to cross off the list.
does the car have EGR valve? maybe the rubber material is torn and your friend have a major vacuum leak, plus exhaust smell you described?
Yep. It still does. Im waiting on a frien to bring me a fuel pressure guage. I just want to make sure the fuel pressure isnt to high for some reason. I dont see any gas in the vacuum tube of the fuel pressure regulator. I have replaced the plugs, wires and installef a new distributor and MAF. My friend had already bought all of this stuff. I had to leave out the bottom bolt of the tps switch to get the correct reading of .54. I tried 2 different tps switches and both show the exact same readings. The idle screw still has the cap on it so i dont want to mess with that if possible. Thanks for the tip on the EGR valve! I will definitely check that out.
Did a fuel pressure test and a fuel leakdown test. Both look good. Found vacuum hose to fuel pressure regulator to be split in half so replaced that with a new vacuum line. Its idling and seems to be running a little better... but the fumes coming out of the exhaust are awful. Its not blue like oil and doesnt smell like coolant. Sooty black crap hits the floor and the whitish smoke burns the crap out of my eyes. I smell no fuel. All plugs were sooty dry black when i took them out. The car has been setting for a long time(years)... maybe bad gas in tank? Gonna put fresh fuel in tank and run it a few miles tomorrow to see if that helps or shows me a new problem. Also gonna note coolant and oil levels before i start it up. Ill keep updating this until the car is running correctly... could be a while at this pace.lol
GTA finally able to idle halfway so I drove it to the Shell station, added a bottle of Lucas Deep Cleaning fuel system cleaner and refilled with premium V-Power 93 octane. The more I drove it the better it ran and bad fumes seem to be going away quickly. I'm thinking the old gas has been a lot of the problem with fumes... at least I'm hoping that. This car is soooo solid. Plenty of power with the ride and handling of a brand new car. Scanner showing code 36 (burnoff) and code 33 (maf too high). Cruise control also not working. When I got back a friend brought over his smoke machine to check for any vacuum leaks I may have missed. The only smoke is coming out of the throttle body areas where the shaft goes through the body(both sides of throttle body... linkage area and tps area). Is this normal to leak some? The car only has 60,000 miles. I can't believe it should be linking this much. I'm gonna smoke my 89 formula tomorrow to see if it smokes any in the same areas.
You know... it is a brand new MAF but the last mechanic put in on and who knows where it was setting around prior to that. I have a can of MAF cleaner... I'll clean her tomorrow. Thanks for the suggestion. Can't hurt to clean it.
I hooked smoke machine up to my formula. Smoke leaks in the same exact areas so I'll assume that's normal for these cars. I'll check resistance on the fuel injectors tomorrow to make sure they are with 15.8 to 16.6 just to rule that out.
Checked timing with engine warmed up to 190 degrees. Still setting dead on 6 degrees with wire unplugged but did bounce between 6 degrees and about 12 degrees for a minute or so before settling down to 6 degrees.
Changed oil and filter.
Cleaned MAF. Removed, cleaned up and switched both relays located on drivers firewall. Still getting code 36. I'll probably switch my relays from my formula to this car tomorrow to see if it helps. I'll also unplug the MAF to see if that changes anything.
Idle is bouncing some 950 to 1,100 in park. 600 to 850 in drive. Can get in the car and drive it anywhere without any problem. But just setting in the garage... it drives me nuts bouncing around. Both idles were higher by about another 150 rpms but against my better judgement I removed the idle air plug and lowered the idle (and reset the tps). Noticed a little more of a hard start after doing this. I measured the screw (.200) before I backed it off. I can put it in the same exact spot.
Also see where the EGR duty cycle is always "0" on my scanner. I'll test my formula tomorrow to see if my car ever shows a reading.
The car runs absolutely great! I'd drive it anywhere. Just have to figure out this bouncing idle and code 36 problem.
Repaired headlights today. Swamped in a reman set of new motor assemblies that my friend bought. Easy job.
While the fumes weren't bad after it warmed up the other day. Back to the bad fumes on this cold start today.
Put relays from my formula in this GTA with no difference other than not only is code 36 (burnoff) still coming on... code 33(MAF high) coming on as well... gonna put my MAF on this car tomorrow... the MAF is new but who knows (its a Walker MAF)... I'll also check the volts coming into the MAF if I can figure out how.
Unplugged MAF and noticed the idle got better... still way too high but seemed smoother.
Hope you will find whats wrong with the car. Got mine running great this morning after 3 weeks of pulling hair. End up being plastic vacuum lines cracked throughout the car. But you probably do not have cracked lines since you tested with vacuum machine. But double check, especially under the intake plenum (thats where I had most of the lines cracked). That caused my EGR valve not to open. Dont know if you already did that, but try replacing ICM since they like to go bad often.
Oh also my ECU was bad, not the chip itself but ECU, to test I took it out and tapped on it while it was connected and car running, the idle would drop every time i would tap on the casing, cracked solder joints.
Hope you will find whats wrong with the car. Got mine running great this morning after 3 weeks of pulling hair. End up being plastic vacuum lines cracked throughout the car. But you probably do not have cracked lines since you tested with vacuum machine. But double check, especially under the intake plenum (thats where I had most of the lines cracked). That caused my EGR valve not to open. Dont know if you already did that, but try replacing ICM since they like to go bad often.
Oh also my ECU was bad, not the chip itself but ECU, to test I took it out and tapped on it while it was connected and car running, the idle would drop every time i would tap on the casing, cracked solder joints.
A new icm came with the distributor and ive swapped in a good used ecm from another friend that i tested on my formula when the ecm went out in it. Ill check out those vacuum lines again. Glad you got yours running again!
Cruise control not working so pushed smoke into the cruise control. Smoke came out everwhere when hooked up to the large port. Not for sure if this is correct so i just blocked off both vacuum lines that hooked up to the cruise control.
Swaped MAF from my formula over to this car. Immeadiately noticed a difference in closed and open idle(not sure if improvement was from blocking the vacuum lines of swapping the MAF). Idle much smoother. Code 33(maf hi) went away. One thing to note... one of the previous mechanics had lost the MAF bracket. I put mine on the car for now. Not sure if that bracket would help to ground the MAF in some way. Obviously it would keep the MAF secured better with less bouncing but not sure if that even matters.
After warming the car up I unhooked wire and checked time. Note were earlier in this thread the timing was jumping from 6 to about 12 the settled on 6. Well... this time it was a steady 12 degrees. I adjusted back down to 6 and engine smoothed out some more.
Set the idle using the instuctions from the link earlier. Last time i did this i couldnt get the idle to adjust down past 650rpm in gear. This time it went well below the 450 mark and had to bring it up but after hooking IAC back up idle was back up to 900 when in gear. So i had to adust the idle screw back down as far as it will go and adjust the tps accordingly. Now when in gear the rpms are around 750. Entirely driveable and runs well like this but still not quite right.
Also note earlier I mentioned that the passenger side electric fan would run non stop. One time I turned the a/c button off on the console and it turned the fan off but ever since it its been running non stop. I figured i had bigger fish to fry so i havent been worried about it. But i just realized as i was finishing up that my code reader is shown an a/c request signal which would turn on that fan. I need to figure out that problem. Maybe it will let the idle speed come down more?
Car continues to run better with the exception of Code 36. I used this flow chart to help with it. http://www.chevythunder.com/maf_code_36.htm
Thought we had fixed it after finding a short in the black wire running from the ECM to the power relay. The code went away for 10 starts but then appeared again.
Still have some other problems to fix as well...
Car runs just a little rich (no where near as bad as before).
If I have run it for say 40 minutes or so the idle starts surging a little.
Cruise control still doesn't work (it has vacuum going into it but I haven't looked any further than that)
Steering wheel radio buttons work sometimes and sometimes not. I removed the pad and slightly jiggled around wires. That seemed to help. Found this article and will check into it more. https://www.thirdgen.org/forums/car-...-controls.html
Climate control fan only works on high. Its one of the push button types... I haven't looked into it much further yet.
Electric fan on passenger side continues to run all the time. I can unplug the temp switch located on the passenger side head, the pressure switch on the condenser and remove the fuse to the ac/heater and the fan still runs. The only time it will stop is if I unplug the relay. Swapped relays but fan still runs. I'm thinking its the climate control unit.
11-02-2016, 10:46 PM
Another weird thing is the passenger fan never goes off. It runs all the time.
