Help! odd problem- ugly startup, then runs OK until hot, then stumbles and backfire

BoostMasterK

2 boys now, need more GNs
Joined
May 28, 2001
This is aggravating me for several weeks...basically since it got very hot outside. 87 TB

On cold start it gives me trouble: starts right away but very ugly stumbling idle for a minute or so, then it settles right down to normal. I drive away and everything seems fine.

As it's warming up, no problem I can give 15psi with no pop, miss etc. Then when it gets good and warm...like coolant 180+ it will start to sputter under fairly light loads...heavier throttle doesn't seem to bother it. BUT then it gets worse until I finally have to limp it home. It hasn't stranded me yet though, it will always start back up. The next morning on cold start, same scenario.

On WARM starts (like if I drive the car somewhere, park it in the sun and it "heat soaks") the stumbling situation will come on much quicker. In fact, sometimes immediately. If I try to "push through it" it will pop and stall out. I have to ease into it and limp home.

There are no ECM codes. I've checked/swapped pretty much everything I could think of including: plugs, wires, module, coilpack, EGR valve & solenoid, MAF, ECM, chip, looked for vac leaks, checked fuel pressure, etc.

Ideas left to try/check: cam sensor, crank sensor, sticky fuel regulator/leaking injectors...

I've heard a cam sensor failure can behave that way but I would expect trouble starting it (?) Same with crank sensor (?)


Any input appreciated! TIA!!
 
Do you have a voltage gauge hooked-up or a scanmaster to monitor the voltage while driving.

How old is your battery and alternator? you can have them checked for free at auto parts stores, i know autozone and advanceautoparts have a test unit they roll out to your car and can test them,only takes a few minutes.

The only reason i suggest this is i recently read in one of the threads here were someone was having a simular problem and it ended up being the battery,it would drop to something like 9 volts while driving.
 
Battery is a year or two and cranks the car solid, immediately.

Alternator is original with 25K miles. Voltage is OK at idle but just to be sure I will check the DS again to see what it was before the stall. When it stalls it starts right back up again though.

thanks and keep'm coming
 
Well it seems it was the cam sensor. The "key" on the ring inside was broken and it was floating around in there. I didn't get a chance to road-test it tonight, but it started right up. :biggrin:
 
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