Hey guys, first-time poster here. I've been troubleshooting my 88 Fox 5.0 for the past few days after randomly my idle became very rough, fluctuating rapidly between 700-900 RPM needle all over the place. In addition, the car shakes and thumps very badly when accelerating at the low end, not as bad higher but not normal either. When at idle the car smells very rich like unburned gas. I've put in a new IAC, done base idle resets, and verified the TPS voltage. I don't believe there is a vacuum leak; my spark plugs look okay, and the fuel pump primes when the key is turned. Speaking on the base idle reset when adding accessories, the car does not want to run, and the problem of sputtering and roughness returns. On the initial start for the day, the car runs fine, but once the car gets to around 180-200 degrees, problems start. I believe the car has a mild cam and MSD distributor and ignition (done by the previous owner). Not too sure where to go from here. I was thinking the TFI Module on the distributor because it seems to be missing and only after it's warmed up. The cap and rotor look okay; I did buff them up a little as well, same with the plugs. I did run the code reader as well and most of the time got 11, 10 ,11 but my father did it once and got 14, 66, and 96. I try to do a running test, and the car almost chokes and clicks, and the reader turns off, and the engine goes low. I looked the codes up, and they didn't make a whole lot of sense. I know the MAF sensor is clean. I did take it out to inspect it, the same with the throttle body stock intake too. I'm wondering if it could be a stuck or leaky injector or EGR valve. IDK, but I don't want to have to take apart my whole car with no vision (daily driver). Thank you in advance for replies!
Engine Rough idle and aggressive sputtering when accelerating
- Thread starter 88vertible
- Start date
89notchDude
Active Member
Unplug the iac and see if the problem persisits. If you have a stock ECU, maybe have it sent out to ECUexhange for peace of mind.
Was the car converted to mass air or was it originally a California car? Reason I ask is mass air was not on all the Mustangs until 1989 and only the 1988 California cars got it.
Code 14 is the PIP in the distributor
Post in thread 'Error Code 14, what does it mean?'
https://stangnet.com/mustang-forums/threads/error-code-14-what-does-it-mean.751638/post-7508908
Code 66 is MAF below minimum test voltage.
Post in thread 'Code 66 Help!!!'
https://stangnet.com/mustang-forums/threads/code-66-help.900471/post-9078317
Code 96 is the fuel pump circuit showing no power.
Post in thread 'Code 96 Repair:'
https://stangnet.com/mustang-forums/threads/code-96-repair.835140/post-8412258
First one points to the distributor, second one pints to the MAF, and third one could be if the car was converted to mass air they did not wire this up.
The MSD distributors are great mechanically. The electronics suck. I would find a good PIP and TFI and swap those out. Plenty of discussions on here as to what brand and part number to buy.
I will say (what @89notchDude is alluding to) is these ECU’s are 30+ years old. They have components that are past their end of life so it would be a good idea to send it off to be repaired. ECU Exchange has done several of them for members on here with great results.
www.theecuexchange.com
Code 14 is the PIP in the distributor
Post in thread 'Error Code 14, what does it mean?'
https://stangnet.com/mustang-forums/threads/error-code-14-what-does-it-mean.751638/post-7508908
Code 66 is MAF below minimum test voltage.
Post in thread 'Code 66 Help!!!'
https://stangnet.com/mustang-forums/threads/code-66-help.900471/post-9078317
Code 96 is the fuel pump circuit showing no power.
Post in thread 'Code 96 Repair:'
https://stangnet.com/mustang-forums/threads/code-96-repair.835140/post-8412258
First one points to the distributor, second one pints to the MAF, and third one could be if the car was converted to mass air they did not wire this up.
The MSD distributors are great mechanically. The electronics suck. I would find a good PIP and TFI and swap those out. Plenty of discussions on here as to what brand and part number to buy.
I will say (what @89notchDude is alluding to) is these ECU’s are 30+ years old. They have components that are past their end of life so it would be a good idea to send it off to be repaired. ECU Exchange has done several of them for members on here with great results.
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There’s so many things it could be.
1. I was having the same problems and it ended up being a plug wire arcing to the head. I didn’t see it until I ran it at night and looked. Showed up right away in the dark.
2. If your ECU is old send it to ECUEXCHANGE for a rebuild. They don’t charge much and they’ll replace all the capacitors and fix anything else that is wrong.
3. TFI could be bad
4. Do a smoke test on the engine. That’ll show any vacuum leaks.
5. As a last resort take it to a mechanic who is known for working on a foxbody.
