97 Transport backfiring instead of starting

[tobas]

After an initial start (without problem) if van restarted it will backfire instead of starting. This happens intermittently and may backfire once, twice, even up to five times before actually starting...Any ideas?

[LMP]

ALl severe causes put aside (like burnt valve), backfiring is generally associated with lean mixture. THe first start comes after injector 2 sec "priming" so this one is obviously rich mixture. But the following starts, when they occur right after the first or/and without turning the key to OFF, have no primer so "for some freak reason", they could be lean and lead to backfiring.
THIs being said..I can't advance definite explanations. Coolant temp sensor could be a factor.
..You did not say why/how it would stop after first starting normally..does it stop by itself or you do it on purpose?
..ANd does the car exhibit other abnormal symptoms ?

[tobas]

The backfiring occurs after the engine has been turned off and then when restarted. This can happen immediately after shutting it off or after 10-15 minutes. Van would still be somewhat hot, not entirely cold engine. Doesn't seem to do it when engine is cold. In terms of any other symptoms, engine does surge on occasion? ?MAP sensor was replaced to combat this issue per mechanic's recommendation when scanned but did not solve the problem. Could a vacuum leak be causing the surge and perhaps the lean fuel mixture (as you suggest) which may be resulting in the backfire?
The coolant temp. sensor was replaced approx 6 months ago but the van was doing the backfiring even then.

[LMP]

Air intrusion due to leaking intake manifold gasket is indeed reported as a cause for issues like you describe.

[tobas]

Thanks for the input...Just a side note to the surging, it can be controlled (stopped) by turning on the a/c or defrost, would that also be relative to a leaking intake gasket? At approx. 100km/hr you can feel slight jerking or that the van is being held back. If speed is decreased or increased it will correct itself. Would that be related to the EGR or perhaps as you suggest, a leaking intake gasket?

[LMP]

It is possible that more than one upset is occurring. a/c makes an additional load on the engine and can dampen the urge to overrev. def and def/flr mix both turn the a/c ON. Parasitic air intake uses "rich" mixture condition at startup to run faster.
egr action is detectable in some conditions, specially going uphill in my case. Nor necessarily a egr "problem", just occurs to act at that time .

[tobas]

Any thoughts on the TPS as I have heard that the engine may display similar symptoms to a bad MAP sensor? Not displaying a code for this, just curious.

[LMP]

TPS pops codes very easily...and that disables 4th, TCC and cruise.......

[tobas]

OK, thanks. I guess I'm back to the original suggestion about a possible intake leak (not what I wanted to hear) and I will go from there.