No Start

[shoson]

Well, on my 94 mtx with 153k doing a little maintenance and work to pass emmissions and now the car won't start. I replaced the starter and both 02 sensors. Checked and car started ok. Then changed tstat, ect, temp sender and lubed the throttle cable (was rock hard).

Went to start to check for any coolant leaks and it would not start. Tried to start and stepped on the gas and it started, ran real rough with a fair amount of black smoke from the exhaust. Pulled codes and I got a 157 and 542. Didn't think the maf sensor would prevent it from starting but I switched the maf from my 93 atx and same problem, no start unless I step on the gas. The mtx maf ran ok in the atx. When I turn the key the tach does move. The cel glows brightly but does not stay on. Since there's not a whole lot of room I thought maybe I disonnected an electrical or vacuum connection. So looking around I did find a vacuum hose off (the hose ran from top of manifold next to throttle body) down to a t connector and the other part of the t was disconnected. Did wiggle test on wires. Still no start. So I have spark and fuel, since It will run, although poorly, but both when only stepping on the gas and then runs poorly, if I take my foot off the gas pedal it stalls out.

Can't think of what I'm overlooking. She's my daily driver, so any help is appreciated.

 

[Mr Anonymous]

Did you adjust the idle stop screw on the TB by any chance (you're not supposed to...)? Also, is it possible that the throttle cable is binding and keeping the plate slightly open? A couple of things to check anyway.

 

[shoson]

No, I din't touch the idle set. The plate is shut all the way so the cable is probably not binding, but easy enough to take off and re-check. Thanks.

 

[projectSHO89]

Since it will run with your foot on the gas, the problem is the IAC valve. It is responsible for providing air when the throttle plate is closed.

Check to make sure you hooked it back up.

Once you get that resolved, try to start the engine with the MAF disconnected. If it runs better or runs properly, the MAF or its wiring is suspect.

Steve

 

[shoson]

Thanks. I never took the iac off, but had made sure it was hooked up ok when checking all the connections in that area. Forgot to mention in the original post too that when I switched maf between the two cars I also started each with the maf disconnected. No difference. You made me think again about the iac, so I disconnected the battery again (first time for starter install), turned on the lights, waited and re-connected it with the idea of doing an idle reset. Didn't work, still cranks but no start without foot on the gas and then it will stall if I take my foot off. Would the iac just go bad without any symptoms? I had no idle probelms before this.

 

[shoson]

OK, I replaced the iac. What a pita. It seemed to take forever to get that bottom screw back on. I also took off the throttle cable and put it back on in case it was kinked or something. Still no start. However, it does seem to almost catch when cranking, so it is better than before. It will still start when I step on the gas. When cranking it and manually moving the throttle under the hood it seems to be so close, it's like a business card width between the throttle stop screw where it will crank and start. But no, I didn't move the stop screw setting for the idle. Cleared the codes and rechecked still getting 157 and 542. 542 I assume is from the stalling. The maf signal low, I'm not sure. Had the same symptoms when I switched the maf between two cars and also unplugged them. Would an adjustement to the tps possibly help? or sould I be paying more attention to the 157 maf code? Just frustrating to figure out what's going on since I, or thought I didn't do anything besides the tstat, ect and temp sender to have this problem pop up without any prior similar problems.