Hesitation and stuttering during idle/acceleration

[drotara]

Hey all,

I have a 1990 Gen 1 SHO 160K miles and it was running great until one day I noticed that it stuttered and then it progressively got worse. Now it seems like when it is under load / accelerating it stutters and seems to really struggle. Once I get above 3 - 3.5K rpms it doesn't have any of these issues anymore. It almost acts like i'm lugging the engine when at low rpms. Before this happened I did have a small trace of gas while driving but that seems to be gone now, although I don't drive it as much because of this issue.

Issue:
- Rough idle and can see on tac fluctuate <100 rpm
- While accelerating at low RPMs the car will hesitate / jump and seems like it completely misses. This is usually between 1k-2500 RPMs then at higher RPMs it steadies out.

Replaced:
MAF sensor
DIS sensor (mechanic recommended replacing this)
TPS
Cam shaft positioning sensor

My spark plugs are relatively new (<10k miles) and clean. Fuel pressure was checked and said it was okay. It doesn't have any problems starting up while hot or cold. Has anyone experienced this issue or have any idea what is going on I would greatly appreciate it!

Thanks,

Alex

 

[rubydist]

First thing, always pull the codes.

If you don't have the info on how, go here:
http://www.troublecodes.net/ford/

btw, it is better to count the flashing light than to try a code reader, because the obd1 code readers were notoriously not reliable.

Tell us what the codes are. That will help us help you.

 

[drotara]

Oh yeah I forgot to mention that I tried to get error codes and there are none. with both KOER and KOEO and they all flashed 11.

 

[SHOMON]

Does this car have superchip plugged into the computer? My old ATX did this when the chip took a dump. I replaced all the same parts as you plus the fuel pump!

 

[drotara]

I had a chip on the MAF but I removed it a while ago like 1 year ago. Did you just take the chip out to fix your problem?

I forgot to mention that I have reset the computer by unplugging the battery and pushing the break for 1min or more and it does seem to help with the idle but as soon as I start to road test it the symptoms do come back slowly.

 

[SHOdded]

Insufficient airflow for some reason? Checked grounds? Hopefully codes will provide direction.

 

[drotara]

First thing, always pull the codes.

If you don't have the info on how, go here:
http://www.troublecodes.net/ford/

btw, it is better to count the flashing light than to try a code reader, because the obd1 code readers were notoriously not reliable.

Tell us what the codes are. That will help us help you.

Oh yeah I forgot to mention that I tried to get error codes and there are none. with both KOER and KOEO and they all flashed 11.

 

[rubydist]

so if there are no codes, but when you reset the pcm it runs better for a while and then gets progressively worse, I suspect that the oxy sensors are going bad, and are failing in such a way that the mixture gets too lean. At this point, I would change the oxy sensors.

 

[drotara]

Alright I will update this thread once I have checked the grounds (specially the DIS one as the mechanic said he was seeing funky stuff there) and if that doesn't work I will replace my O2 sensors. Thanks guys!

 

[reags8]

Following .... I have a studder/hesitation similar ....