help engine miss iv tryed everything

jldtoker

Registered User
i have a 93 thunderbird sc auto. If i drive the car normaly theres not a problem and it idels fine but when you put into it and gunn it, it misses horabliy sounds kinda like a sputtering sound and shakes the whole car. iv changed plugs, wires, fuel filter, MAS, TPS, pcv valve, ingnition modualr, coil pack, nothing has worked and i got the fuel pressure tested and its fine, and the motor mounts are still good. the only thing i can think of is maybe bad injectors but if anyone has a good ideal please let me know its driving me crazy not being able to fix it and its been running like this for 4 months now iv just parked the car since i couldnt figure out the problem.
 
My $0.02

Could be a vacuum leak somewhere in the supercharger "plumbing". It doesn't take much to make the car stumble under acceleration. Even if you have checked and double-checked, it is very difficult to get every connection sealed. I finally invested in a set of teflon gaskets for the top and tubes (from TinKnocker) and have noticable improvement in boost. I had been using RTV gasket seal and thought it was doing the job, but after installing the gasket set I think differently. They also make it much easier to remove and reinstall the SC parts (no scraping off the old RTV every time you disconnect a fitting).

One more thing... New sparkplugs will sputter in an SC if they are the wrong plugs. Stay away from Bosch. Use Motorcraft or AutoLite Double Platinums for best performance...
 
Is it possible you may have a bad batch of gas? Has the car been sitting for a while? Sounds like you have put some serious time and $ into this problem. As previously mentioned, check for vaccum leaks. Spray some Carb cleaner around the SC top and inlet plenum. Check the intercooler pipe connections also. Make sure they are tight, and spray em down also. If the cars idle changes while spraying, you found a culprit (very well could be more than one leak). As a last resort for finding vaccum leaks, bring it to a shop that has a smoke machine and make sure they know how to use it properly. This test will show off every vaccum leak you have, even in the hardest to check places. Good luck!

-Mike
 
well after we installed the new plugs and that didnt help i took some orinal ones out of another sc and it still didnt help as far as bad gass i drove the car for about 2 months or better with it like that and iv went through plunty of gass and im pretty sure theres not a vac leak but i have yet to spray down all the tubes and stuf but even if it was a minor vac leak it wouldnt make it act this bad. could it be a possiblity of bad injectors iv put fuel injector cleaner in several times and it seems to help but still always has the bad hessatation. thanks for your oppions tho i appreciate it im at a loss on what to do.
 
How old is your fuel pump? They might give you correct pressure at idle but how about wot? Lets just say I have had a lot of these cars and chased down alot of problems like this. These pumps when they get old just cant keep up. Not to hard to change and you might want to go bigger. Never had a bad injector yet.
 
the plugs and wires are only about 3 months old tryed two diffrent typs of plugs the motorcraft and the orginal out of another t bird. we tested the fuel pump its about 35 at idle and 40 when i rev it up. and o2 sensors wont make a car run this bad.
 
My first 89 xr7 I bought idle nice ...than ran like crap once you gave it gas ...turned out to be fuel filter .... my 90 SC started to stumble ...when it went into boost .. shortly there after ... broke the harmonic balancer.... taking the crank sensor with it ...as soon as that was replace ... it started to stumble again ....and the head gaskets went ...In short check harmonic balancer make sure it's not wobbling ..and running true ..if it's doing the wobble ...they tend to break/crack on the collar on the crank and hits the crank sensor ...check the bolt in the end of the crank is still there ...and tight and balancer hasn't walk forward off the crank ....hopefully it's just a vacuum/boost leak ....dave
 
Never had a problem with Bosch O2 sensors unless you dump coolant on them, and with your problem 2 things come to mind.

Fuel pressure can't keep up so you run lean because of a tired old fuel pump. Normal operation should have around 38psi fuel in vacuum, and going into boost you should see an increase psi to psi. So if your hitting 10psi boost, you should see 48psi fuel. This is a requirement or your car can't push out the fuel amount its expecting to for the AFR it wants.

Vacuum leak or Boost leak... 2 different animals. You can have perfect vacuum, but have a BAD boost leak.
 
Back
Top