Engine stumble when the gas pedal is nail ..
#1
Three Wheelin'
Thread Starter
Engine stumble when the gas pedal is nail ..
This is the last thing on my repair list (at least for this year...)
When in neutral, if I quickly nail the gas the engine hesitates/stumbles for a second then revs up nicely. If I nail it quick enough then let off, I can have my foot off the pedal before the engine has a chance to get going. If put my foot slowly (normally ) on the pedal to bring it off idle, it respond normally. Bringing the engine just off idle, then nailing the gas results in good response though. What gives?
When in neutral, if I quickly nail the gas the engine hesitates/stumbles for a second then revs up nicely. If I nail it quick enough then let off, I can have my foot off the pedal before the engine has a chance to get going. If put my foot slowly (normally ) on the pedal to bring it off idle, it respond normally. Bringing the engine just off idle, then nailing the gas results in good response though. What gives?
#4
Three Wheelin'
Thread Starter
#5
Three Wheelin'
Thread Starter
#6
Sounds like bad MAF or nice air leaks. Check your hoses under the intake and the Y connectors at the MAF boot.
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#8
Three Wheelin'
I have exactly the same issue. They're like little backfires. I swapped for a good MAF and those symptoms went away, including my acceleration became crispier. So instead of replacing/rebuilding the MAF I am contemplating going to the MAF-less Alpha N from JDS after I've saved up for it.
#9
Rennlist Member
Well it should be good for 75k miles or so...... the symptoms you are getting are of a weka mixture when the LH goes open loop to allow acceleration enrichment. Too little enrichment and you get the hickups :-)
So look for airleaks into the intake as Sean suggests - check engine vacuum on the front damper at idle - should be around 21"Hg at sea level.
Check fuel pressure, check temp 2 sensor....
So look for airleaks into the intake as Sean suggests - check engine vacuum on the front damper at idle - should be around 21"Hg at sea level.
Check fuel pressure, check temp 2 sensor....
#10
Rennlist Member
Luc.........first, make sure all the basics are covered; spark plugs, disti caps and rotors, air and fuel filters.
As Sean suggests look for vacuum/air leaks, fuel pressure etc.
Did you install the PEMs? how old are the injectors?
As Sean suggests look for vacuum/air leaks, fuel pressure etc.
Did you install the PEMs? how old are the injectors?
#11
Racer
Join Date: May 2012
Location: Monroe, NY 10950
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I was having this problem, I pulled the MAF and noticed the black plastic cover had some minor pits from the engine heat. It was also not sealed well at all as I could easily remove the cover with basically no effort. I sealed the cover shut with clear silicone as well as filled in the pits with silicone and it solved the problem completely. I guess it was allowing unmetered air to get in.
#14
Three Wheelin'
Thread Starter
How was the trip to Kansas ?
Plugs and wires changed this spring, Distributors and rotors have less than 10,000 miles (checked also this spring) fuel filter changed 2 years ago. Air filter is almost new. O2 sensor changed 3 years ago with OE Bosch unit
I will recheck, as Sean suggests, fuel pressure and air leaks but when I checked those a couple of weeks ago, pressure was good (I have a fuel rail gauge) and vacuum was steady at 20 Hg. I also check the fuel pressure regulator (removed the vacuum line and fuel pressure rise witch is normal) and dampers (no fuel smell or leaks).
I don't know if this is related but when driving around town, idle speed is not obtain instantly when in neutral - it stays at 900-1000 RPM for a few seconds than drop to 675-700 RPM. Idle is stable.
PEMs are installed. Concerning the injectors, I don't know. Looks original.
The only modification is a x-pipe without cats.
#15
Rennlist Member
I am following this with interest. I have the same symptoms - a bit of "delay/stumble" when blipping the throttle from idle in neutral. I have no "popping/backfire". I also have a slight miss just off idle ~1,200 - 1,500 rpms, which results in slight "bucking" while driving at low RPM, say in a parking lot. Very smooth and resposive otherwise.
Newly rebuilt MAF, new rubber boots (MAF, throttle body, intake runners), newly cleaned/tested injectors, new caps, rotors, Beru plug wires, plugs. Symptoms were present before all of this recent work.
My car is a 16v Euro LH, bone stock, no cats or o2 sensor. It does not do this when engine is cold, only when warm. I am thinking it is a bit lean just off idle.
Looking forward to what you find.
Newly rebuilt MAF, new rubber boots (MAF, throttle body, intake runners), newly cleaned/tested injectors, new caps, rotors, Beru plug wires, plugs. Symptoms were present before all of this recent work.
My car is a 16v Euro LH, bone stock, no cats or o2 sensor. It does not do this when engine is cold, only when warm. I am thinking it is a bit lean just off idle.
Looking forward to what you find.