1987 C4 running rich
Thread Starter
4th Gear
Joined: Oct 2022
Posts: 4
Likes: 0
1987 C4 running rich
Hello everyone, I have a 1987 C4 that’s I recently bought (61k miles). When I bought it had code 34 and 45 and it was running really rich. Since then I put a new maf sensor on it and replaced the fuel pressure regulator the previous owner had had also just replaced all the injectors. Now it has code 36 and occasionally 45 also the exhaust still smells really rich
Any idea of what I could do to fix this,
thanks
Any idea of what I could do to fix this,
thanks
Melting Slicks
Joined: Sep 2010
Posts: 2,422
Likes: 202
This code 45 can lead to a repetitive loop.
Clear the ECM
If the code 36 & 45 return. Round robin diagnosis.
Injectors are the same.?
MAF is genuine.?
Possible EGR
Check for pinched/ shorted wires.
Check vacuum pressure with a guage. Inspect for V leaks.
Do you have a scan tool?
Confirm TPS voltage.
Monitor O2 for erratic readings.
Check IAC Counts
This will keep you busy for a few min.
Clear the ECM
If the code 36 & 45 return. Round robin diagnosis.
Injectors are the same.?
MAF is genuine.?
Possible EGR
Check for pinched/ shorted wires.
Check vacuum pressure with a guage. Inspect for V leaks.
Do you have a scan tool?
Confirm TPS voltage.
Monitor O2 for erratic readings.
Check IAC Counts
This will keep you busy for a few min.
Thread Starter
4th Gear
Joined: Oct 2022
Posts: 4
Likes: 0
Thank you for your response,
I have cleared the codes by disconnecting the battery normally the maf code comes back almost immediately and like I said code 45 will come on and off.(occasionally while driving the check engine light will just shut off)
I’m pretty sure the injectors that were put in the car are the same although I’m not positive.
The maf that I put on is not genuine although it did seem to help the car run better.
ive checked for pinched/shorted lines and found nothing.
I forgot to mention that the o2 sensors were replaced recently by the previous owner.
I do not have a scan tool.
and I will check the vacuum pressure, tps voltage and iac counts.
Thanks
I have cleared the codes by disconnecting the battery normally the maf code comes back almost immediately and like I said code 45 will come on and off.(occasionally while driving the check engine light will just shut off)
I’m pretty sure the injectors that were put in the car are the same although I’m not positive.
The maf that I put on is not genuine although it did seem to help the car run better.
ive checked for pinched/shorted lines and found nothing.
I forgot to mention that the o2 sensors were replaced recently by the previous owner.
I do not have a scan tool.
and I will check the vacuum pressure, tps voltage and iac counts.
Thanks
Drifting
Joined: Nov 2015
Posts: 1,707
Likes: 328
Finalist 2020 C4 of the Year - Unmodified
For code 36, this is the MAF burn off circuit. Many replacement MAFs don't have this circuit; you can spend $600 for the OEM style to make sure you get one with burn circuit, I'd rather save the $400 or so myself. The other MAFs typically work fine, the "fix" for those is to have your ECU MEMCAL changed to disable code 36 check, by a tuner or similar.
Key, all the burn circuit does is clean the MAF sensor. This was required in the original MAF. Typical replacements are designed such that annual cleaning is fine.
The nasty with code 36 is it only triggers after code reset when the engine has started, reached normal operating temp (open look) and the ignition is turned off. This is when the burn circuit is activated, so if it fails, code 36 is shown on next start.
Search the forums for "code 36", several good threads regarding this.
Key, all the burn circuit does is clean the MAF sensor. This was required in the original MAF. Typical replacements are designed such that annual cleaning is fine.
The nasty with code 36 is it only triggers after code reset when the engine has started, reached normal operating temp (open look) and the ignition is turned off. This is when the burn circuit is activated, so if it fails, code 36 is shown on next start.
Search the forums for "code 36", several good threads regarding this.
Thread Starter
4th Gear
Joined: Oct 2022
Posts: 4
Likes: 0
So I checked my tps sensor at idle it read 2.5volts and at full throttle4.5 I also checked that vacuum all looked good there except I notice that the egr valve Under the intake has no vacuum(I’m not sure if that’s normal).
I keep thinking something is computer related because just about every time I check the codes there different. For instance today after a 30 min ride code 33 came up randomly along with 36 & 45 again
but yesterday I only had 36
I keep thinking something is computer related because just about every time I check the codes there different. For instance today after a 30 min ride code 33 came up randomly along with 36 & 45 again
but yesterday I only had 36
Drifting
Joined: Nov 2015
Posts: 1,707
Likes: 328
Finalist 2020 C4 of the Year - Unmodified
TPS sensor needs adjusted, it should be around .54V (0.54V) at idle (engine doesn't need to be running to check). Weird, 2.5V should call for half throttle.
When code 36 is in place (most codes for that matter), the ECU (computer) stops making dynamic changes (fuel mix and a bunch of other stuff), instead goes to static "standard" setup. Have the clear the codes (ie no SES light) to stop this.
When code 36 is in place (most codes for that matter), the ECU (computer) stops making dynamic changes (fuel mix and a bunch of other stuff), instead goes to static "standard" setup. Have the clear the codes (ie no SES light) to stop this.
Drifting
Joined: Nov 2015
Posts: 1,707
Likes: 328
Finalist 2020 C4 of the Year - Unmodified
Clear codes: Disconnect the battery for 15-30 seconds.
Adjust TPS: Assuming you know where it's at, there are two screws holding it in place, top and bottom. Note the "holes" allow moving it around. Loosen screws enough to allow adjustment. Put voltage meter in place for TPS, turn ignition on (DON'T START) and adjust TPS until voltage is around .54V. Check that WOT gets to around 4.5V. Then tighten the screws and re-check.
Adjust TPS: Assuming you know where it's at, there are two screws holding it in place, top and bottom. Note the "holes" allow moving it around. Loosen screws enough to allow adjustment. Put voltage meter in place for TPS, turn ignition on (DON'T START) and adjust TPS until voltage is around .54V. Check that WOT gets to around 4.5V. Then tighten the screws and re-check.
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