1G Idles, but stalls on throttle.

[DroopYeyeS]

Ok guys, someone give me some more ideas please. "91 talon bone stock except for walbro 190 pump. Ijust started looking at this car last week on the week ends. The car will start and idle great but the instant I give it ANY throttle it boggs and stalls out. I have replaced the ECU, MPI, CAS, and TPS with know good pieces and the issue persists. The fuel pump is brand new and is running. I have check the Timing and compression, both of which check out fine. ANY ideas at this point would be welcome to give me somewhere else to start looking for the issue.

 

[rush2252]

Boost leak. I bet it wont run over 2k when you try to drive it correct? It sounds like huge boost leak to me. Thats always the first thing I check when one acts like that.

Kolby

 

[DroopYeyeS]

I wish it were that simple. this thing wont run at 900rpm if I even move the throttle plate 1/16 of an in. It stalls the second the plate opens

 

[rush2252]

again still sounds like a boost leak. If your base timing is correct you have compression and fuel then it almost has to be a major pre TB boost leak hands down. You stated you checked the ECU already correct? If so boost leak test at 20PSI and post your results

Kolby

 

[DroopYeyeS]

I'll give it a go inthe morning and see what happens.

 

[DroopYeyeS]

Now that I'm more sober, , I'm not sure that it could be a boost leak. I'm going to doublecheck it, but this thing stalls out the instant the pedal is even touched, so the system doesn't have time to build any boost what so ever. As I said I am going to check that bu any other ideas out side of a bad ground guys?

 

[SkylinesSuck]

Sounds like the same thing that happens when a MAF goes bad on Nissans. You guys are MAF, not MAP, right? Check the MAF connection, and then maybe swap out a known good one from another car and see if it fixes it.

 

[DroopYeyeS]

Ok, so I've now tried the Maf, and searched for boost leaks. This thing is stalling the very instant the throttle plate opens even a mm. It doesn't even have time to rev, it just stalls. There is no time or delay for a fuel pressure drop, boosting issues, or timing issue. Any ideas guys?? This is a real enigma for me.

 

[gstbuford]

mine was doing that after i left the car sit for a while, turned out it was bad gas. drained the tank put fresh gas and some lucas fuel system cleaner in her and it ran fine. just an idea.

 

[DroopYeyeS]

Ok guys, This thing is still not running right. It will idle all day long, but the instant thethrottle plate opens it starts to stall. I actually experimented with the IC piping this weekend. When the hose from the j pipe to lower ic inlet is off at the IC, the car revs wonderful. Not enough power to drive obviously, but it does rev without stalling. As soon as the hose is back on, it starts to stall again. I've tried everything I can think of guys, I need new ideas. I've borrowed almost every sensor and needed piece from my talon to try on this car, ecu, mpi, tps, cas, coil, igniter, everything I car think of. Any ideas?

 

[rush2252]

Have you double checked the firing order? or used a timing light to set the CAS? And can we get an idea of what happend for the car to get to this state?

Try leaving the hose hooked up and unplugging the MAF. I ran into a similar situation on a 90 model that somebody had wired a 2g MAF into. They retarded the timing with the CAS and adjusted the BISS out to idle the car up. With the MAF plugged in the car would idle but die like your stating. With it unplugged it wouldnt idle for shit but would run otherwise.

 

[jag987]

Now that I'm more sober, , I'm not sure that it could be a boost leak. I'm going to doublecheck it, but this thing stalls out the instant the pedal is even touched, so the system doesn't have time to build any boost what so ever. As I said I am going to check that bu any other ideas out side of a bad ground guys?

If you have a boost leak, it would also be a vacume leak.
while in vacume the car would see less air that is actualy entering the system, and you would be runnign really rich.
while in boost it would see more air than is really there.

A boost leak test is easy. Be a good thing to check off the list.

 

[DroopYeyeS]

All of the above has been done guys. This car sat for about 4 years before a friend bought it. I got it running for that friend, and it ran very well (except the thermo switch was bad and therefore the rad fan wouldn't kick on). Against my advise that friend drove the car, and overheated it causing the radiator to bust the lower seam. The car got parked and sat for another 7 months. So another friend buys it off the first friend who just has lost interest. We tow the car (flatbed) to new owners home, put a fuel pump back in the car, fix the rad issue, fired it up and BAM. Now the issue insues. I have done all the basic TS steps. Compression down to checking ground wires on the harness, all with no glory. I want to scream bad gas, but the car idles wonderful. It almost sounds electrical what ever it is. I say that because the time delay between open of the throttle plate and the engine falling flat is almost none. I am truely stumped. This car went from running fine to now it couldn't out run a rock!

 

[rush2252]

If you have a boost leak, it would also be a vacume leak.
while in vacume the car would see less air that is actualy entering the system, and you would be runnign really rich.
while in boost it would see more air than is really there.

A boost leak test is easy. Be a good thing to check off the list.

Correct almost... Pre Throttle Body is boost leak post throttle body is BOTH.

All of the above has been done guys. This car sat for about 4 years before a friend bought it. I got it running for that friend, and it ran very well (except the thermo switch was bad and therefore the rad fan wouldn't kick on). Against my advise that friend drove the car, and overheated it causing the radiator to bust the lower seam. The car got parked and sat for another 7 months. So another friend buys it off the first friend who just has lost interest. We tow the car (flatbed) to new owners home, put a fuel pump back in the car, fix the rad issue, fired it up and BAM. Now the issue insues. I have done all the basic TS steps. Compression down to checking ground wires on the harness, all with no glory. I want to scream bad gas, but the car idles wonderful. It almost sounds electrical what ever it is. I say that because the time delay between open of the throttle plate and the engine falling flat is almost none. I am truely stumped. This car went from running fine to now it couldn't out run a rock!

http://www.dsmtuners.com/forums/art...guide-compression-test-vs-leak-down-test.html

Try a leak down. I didnt read the overheating issue. Its possible you have a cracked head. Which Calan explains would not effect compression necessarily

 

[chaggard27]

Also I would check the spark plugs after you idle it for a bit. Check to see if any are wet. With it overheating you could have blown a head gasket causing coolant to get into 1 or more of the cylinders. This would cause it to not rev up since not firing on all cylinders.

 

[DroopYeyeS]

I can understand the confusion. As I stated the car did over heat once which did pop the seam on the radiator. Other wise the car is fine. It does not overheat anylonger as I've replaced the radiator, and thermo switch at this point. Rush I'm with you on the leak down idea and have performed this already. Moving beyond all the basics has anyone seen this issue before. Would the egr sticking open be a possible cause for this. I've not replaced that yet. I've replaced all other sensors, plugs, wires, coil, ignitor, pcv, check base timing, compression/leak down test cleaned IC, and pressure tested system. All with no glory. The same problem occurs. Any ideas on fuel delivery issues or do you even think the car could acount for that kind of fuel change in a fraction of a second? Could the o2 sensor be creating bad info to the ecu?

 

[rush2252]

Im afraid the o2 sensor or egr would not effec the motor that much. My 2g has done some test runs without either after a turbo swap. I run no EGR with out any issues.

If your leakdown was good compression was good fuel pressure checked out and plugs/wires are in good shape then it should be running.


It sounds like something is being overlooked this isnt some uber complicated problem. Have you posted any numbers from the tests? Compression leakdown percentage??

 

[bsbllfit7]

I had this problem before with my car and the problem was that the maf pigtail was not plugged into the sensor. I had removed the intake for some reason and upon re inserting it i forgot to plug the sensor in. Recheck all sensors in the car and check for voltages or impedance's or whatever it is ha.

 

[DroopYeyeS]

I'm with you 100% rush. If I have fuel, air, and spark, this should be a no brainer. That is why I'm here asking you guys. The o2 question was more me wondering if the sensor is bad and not sending the needed voltage readings, maybe the ecu doesn't know how to respond. As for the EGR, the question wasn't about wether or not the valve being on the car would effect it, but more along the lines of if it were to stick open and allow air to just escape freely, would that cause the air volume to change very suddenly and effect the intake system? As I said the car runs great at idle, just won't rev. As for compression, it read between 180 - 185 psi across the board. I'd have to redo the leak down but it seems like the rate only raised about psi when the oil was added.

 

[miliman13]

Updates ?!?