Hesitates after startup or restart, warm or cold...

Just wanted to describe a problem I have noticed, and perhaps get some suggestions from you guys... I have heard various versions of things rather like this, so I will first proceed to describe the precise symptoms:

'89 XJ 4.0l FI IL6 non-HO, stock everything, with LOADS of miles...

Engine "stumbles", almost always stalling itself out unless you are there to milk the throttle, within 30 secs after startup. Occurs whenever the engine has ben restarted, if weather is warm or cold, if I just ran it for an hour, or it's been sitting out all night, same thing.

Within the 1st mile, it tries to stall again, sudden dramatic loss of power, then normally a "power surge", as though it has built up fuel or something, even if you take your foot off the throttle when it starts to stall. Doesn't normally stall all the way out this time, but sometimes. Occurs every time after restarting, warm or cold, regardless of rain or shine, etc, etc, etc.

I am thinking this must have some electronic component problem (like a module or something), since everything works fine after 10 minutes and a few miles. If it was a fuel filter, or a loose wire, or a bad ballast resistor, or plugged injectors, etc, I would expect some other symptoms, or that these would even be intermittent, but these are it. I have tried very hard to find other faults, but I haven't found anything else, although I have not gone out and got the codes pulled.

Can anybody help? I am planning to clean the IAC again and check the TPS, but I am rather stumped...

These engines are notorious for loose intake manifold bolts, so perhaps give that a check. Also look for cracked/disconnected vacuum hoses. Good Luck.

Any news on this? Mine is doing the exact same thing.

My 97 has always done this. First time I accelerate and open the throttle past about 30%, it's like it chokes. I let off the pedal, step down again, and it's fine. This is whether hot or cold, after idling to warm or starting off dead cold.

Got me....

DaveD in Canada said:

These engines are notorious for loose intake manifold bolts, so perhaps give that a check.

Click to expand...

I tightened these bolts to stop an oil leak. I didn't make the connection until you mentioned it, but the stumbling problem I was having has gone away. I had attributed it to the warmer weather, but I definately think tightening these bolts was the contributing factor.