Surging, but not under idle

[blk92stangg]

My friend is coming over this Saturday to check on a problem with surging. I haven't had a chance to drive it yet, but he claims it idles perfectly, but seems to surge when cruising around. His engine is stock other than a MAF upgrade, and the usual header, O/R H pipe and flows. Any ideas on what I should check on? I will pull codes this weekend, but in lieu of that any help would be great.

 

[RayBrian]

its probably the MAF then... are the injectors stock? if they are then is the MAF used? or did he buy the MAF calibrated for 19lb injectors, thats whats stock. If the MAF isnt calibrated for the size injector, it will cause idle and/or all sorts of problems throughout the powerband.

 

[blk92stangg]

The MAF is calibrated for 19 pounders, and it ran pretty well for the past months or so since it was installed. Any chance its a bad tps?

 

[87'GTstang]

If it's while cruising, then yes, the tps can develop off-readings and erratic readings sent to the ecu. Check for proper voltage and see what you get. The only problem I see is that the IAC and the tps are related to each other. If the tps read lower, you'de get an under-surge because it tells the IAC to back off (may have the reading higher/lower backward). So i'de almost be inclined to say look elsewhere. But then again, how often is the problem and any conditions or specific speeds it occurs at?

 

[blk92stangg]

Not sure how often or specfic conditions. He's not much of a car guy, so when I ask him stuff like that he's pretty vague. Once I drive it I'll try to give more info. Thanks for the info so far tho!!

 

[BLOWN95GT]

This probably isn't any help but I had the exact same problem when I had my Accel ignition hooked up. When I bypassed it the car ran great.