87 fox code 22

[Showpony87]

Hey guys,
I'm new to this so go easy on me, I have a super clean 87 t-top pulling a code 22 with a really sharp intermittent Miss. It passes emissions. Car runs great other than the sharp Miss every once in awhile. Everything points to the map sensor however I have replaced it three times and it changes nothing, there are no vacuum leaks on a smoke test. This seems to have started when I installed a 75 mm throttle body, the throttle body seems to be leaking a very small amount of antifreeze as these are cooled. My question is does anybody think a code 22 can be caused from a small gasket leak on the throttle body?

 

[89ripper]

Ive had to replace one before....I had no idea how often the sensor itself goes bad. Have you done some testing with the wiring?

 

[Showpony87]

I haven't used my dvm on it but I did replace it with a few new ones, seems like the problem started after the tb was replaced. It was in rough shape when I bought it, timing was retarded 12deg and plug gaps way off. Had to set the idle and put all the smog equipment back on it to get through our BS Colorado emissions. I will check the voltage on the map sensor, just wondering if the throttle body could be the issue. Or maybe a leaky brake booster.

 

[Showpony87]

I put Saleen fader stripes on it, is that the decals you're referring to?

 

[89ripper]

Im a bit unfamiliar with an 87's wiring vs an 89's (which is what I have) but moving the throttle body along with the wiring back around the plenum could have loosened some of it.
Ive screwed around with the throttle sensor wiring and found problems with the salt and pepper shakers near the back. It caused me a lot of driveability issues.

 

[Mustang5L5]

Check the orange/white wire for 5v to ground.

You’d need an occulliscope to further test it, or something like a thexton 127.

If you have 5v you can try testing continuity back to the ECU and make sure the wire isn’t damaged/broken.

Pin 45 is the signal wire. Pin 46 is sensor ground and pin 26 should be 5vRef.

Also. Make sure it’s a current code by erasing all the codes, and doing a few engine cycles and pulling them again.

Make sure the vac line is securely connected to manifold vac

 

[General karthief]

Is the vacuum line to the MAP sensor good?
It is a speed density car right?
Intermittent miss is usually plug, plug wire or cap.
If the spacer is leaking coolant you need to fix that, to see if that is causing the problem just unhook the hoses and plug or loop them together, see if the issue goes away.

 

[Showpony87]

Awesome, thanks guys. Yes it is speed density, I initially thought spark plug or wires as well but the code 22 for the map is throwing me off. Good call on Loopin the vacuum hoses, I'll give that a shot and see if it Smooths out. I did clean the salt and pepper shakers, that actually helped a lot with drivability but didn't fix this one little miss. It was a bit of a journey Getting the correct voltage out of the TPS so maybe I did bump some wires back there. I'll roll up my sleeves and check all the voltage and continuity.

 

[AeroCoupe]

Is it a high rpm miss or just randomly occurs?

 

[Showpony87]

Mainly low RPM and idle, actually doesn't miss at all under heavy throttle

 

[Mcmahst]

What is the vacuum reading at idle? You said you smoke tested it, but I did the same and didn’t find some leaking vacuum valves. The TAB/TAD valves (I’m assuming those were the things you had to put back on), and the vapor canister valve can leak undetected. All 4 (including the EGR regulator) can leak vacuum and not be discovered in a smoke test. They’re easy to test; it will give you peace of mind to completely eliminate that. I say all of this because I chased an idle and off idle miss and it turned out to be a bad TAB and vapor canister valves. Good luck.

 

[General karthief]

Did you check for codes?
you know there could be codes without tripping the CEL?

 

[Showpony87]

Yes, it's a 22. The 87 has a spot on the dash for the check engine light but it is inoperable from the factory on the 5.0. The Vapor canister is probably the only thing I haven't checked but I'll give that a shot. Great advice from everyone, appreciate the help guys!