You check to make sure you don't have a boost leak. Make sure a coupler didn't pop off of an intercooler pipe

Yes boost leak has been done

Its hard to diagnose such a pronounced problem over the internet especially when you have no check engine lights

Throwing parts at a problem isnt an answer

It could be something like a bad ground to the engine, electrical problem, or the ecu going out.

I pulled the day and didn' see any burns or any smell. And it has been re capped. I' at the point of all I can do is throw parts at it or keep dying on the side of the road . I may try the cas next..

Try it with the maf unplugged.

Let your car idle and give the MAF a few knocks. If it changes the way the engine runs or kills the engine, its the MAF. Yesterday I diaged a jeep with a similar issue and it was the crank sensor. But on these cars the MAF is a much more likely culprit. Live data is the best way to catch the issue, but I know you diy'ers with OBD1 cars aren't likely to have that capability.

Your best bet is to catalog. Severe dropouts like this won't be a boost leak. Almost has to be electrical in nature. Being a 2g I'd check crank endplay and the crank sensor. Check all your grounds. Check and make sure the battery isn't hitting the hood. Seen that one. Datalog will point out issues fast also.

I will try these today after work and let you all know. The car has dsmlink v3. Bit I'm in the process of moving houses and I packed my laptop like a dummy.

For my curiosity sake next time your outside in a well lit area take a couple pictures of the engine bay. We might be able to visually inspect for anything out of place

Also what fuel pump are you running and are you still on the stock fuel regulator? Its also possible to over power the stock regulator

Does it only have these problems when the engine is cold or just started, or after it's been running for a while

Will do, 190 that I just replaced. I took off the vacuum line and no fuel came out of it

AlexGsxCummins said:

Will do, 190 that I just replaced. I took off the vacuum line and no fuel came out of it

Click to expand...

The vacuum line should not have fuel in it so that's normal. It should be hooked to the little purge solenoid by the firewall then run back to the intake manifold. Where it goes into the intake manifold, right next to that is a hole for a bolt that should have a ground wire attached to it that runs to the back firewall.

There is also a.cluster of ground cables behind the battery

Inside the car between the kick panels, under the dash, is a ground wire for the ecu. Mine was corroded, my car experienced electrical problems when the ecu went into closed loop. (On 99 models this issue was corrected and the ground was moved to the side mounting point next to the ecu case)


My 98 gst ecu ground




The 99 gst parts car that made me actually look to see where the hell my ground cable was

I think I finally found it...so I did the "tap on MAF" as soon as I tap it. Car dies.. so I said yes!! Started it tapped it again car died. Started it wiggled the connection car died... pulled the connector off and the rubber grommet is missing..so I ordered a new pigtail, think I should replace the whole pig tail or will that little grommet hold the connector steady..

Its usually the MAF itself in my experience, but hopefully you get lucky. I use the tap test as an extra verification when I diagnose a bad MAF at the shop. Data shows me where the the failure to be within parameters is, and if I can get the tap test to work its more peace of mind that Ive found the issue.
Just as an FYI, Ive had dozens of MAFs fail on Mitsus. Its one of the most common problems they come in for. Again, that's in my experience. Thats why I'm in a lot of threads where people are having drivability problems saying to check the MAF and tap on it etc.

well i got a new MAF and it did not fix my issue.. i also tested my wideband 02 and it seems to be working with the gas in a rag trick... cant even drive my car anymore unless MAF is unplugged...

Your profile does not identify your year, but I can tell you our ‘99 acted the same way and we checked every engine sensor and every ground multiple times.

Turned out to be a bad secondary fuel relay which only acted up when the car went to closed loop. If we unplugged the maf, the car would stay in open loop and run. I have a write-up of it in our build thread.

That said, electrical problems can become fuel problems. That’s why I recommend checking fuel pressure whenever there’s an engine problem.

You shouldn’t be able to wiggle your maf connector. Did you ever replace the connector, It’s supposed to clip on.

Try plugging the maf in but unplugging the tps sensor, how did you do your boost leak test?

What kind of MAF did you get? I know it's hard to believe, but I personally have had to try multiple MAFs until I got a good one. They can be difficult parts for aftermarket companies to get right. Try Napa's. Theirs seem to work good.

Backprobe terminal 4 of the connector with the positive probe of the voltmeter and connect the negative to the ground. Turn the key to on but do not start the engine if the voltemeter does not read around 12v. If so check the circuit back to the MFI relay and fusible link.

Backprobe terminal 3, it should read 4.8-5.2v with the key on. If not check the circuit to the ECU.

Backprobe terminal 5 with an ohmmeter and measure the resistance. It should be less than 2 ohms. If not, check the circuit from terminal 5 back to ground.

If none of the above work, the MAS or ECU is dead. Replace it.

- Barometric pressure sensor: With key on, pin 2 should be 3.7-4.3V at 0' altitude and 3.2-3.8V at 3937' altitude.
- Air temp sensor: see attached picture.

Its a gm 3" that I replaced, both with same issue. I replaced the pigtail as well. I will do the tests today after work and try the tps that was also mentioned and report back.

And boost leak test i took off the cai and made a tester and clamped it to the inlet of the turbo, pressure at 20psi had one small leak at tb that got fixed

Mine would do something similar and it turned out to the the Crank Sensor. When the sensor got warm, it stopped working
I took mine out and replaced it with a 1G Black top Cam angle sensor (and harness) and it solved the issue! It really sounds like a Crank sensor or even Cam angle sensor....but it is defiantly electrical in nature.

If you want to test your crank sensor, you need to disconnect the MPI fuse in your car, or disconnect the ignition coil connectors from your ignitor or your coilpacks. You do not want ignition or fuel injection modes working as you manually crank the engine over. The signal wire should be BLUE on the engine harness side, put the negative terminal of your voltmeter at the negative terminal of your battery, and the red lead to your PIN 3 backprobe. Turn the key to the “ON” position but do not attempt to start the car. Now insert a half inch drive and slowly rotate your crankshaft and engine by hand. You can also elect to remove your spark plugs to make this process a little easier on your arm. Once you have turned the crankshaft over enough, you should see your multimeter switch from a full 5 volts to .1 volts as the crank angle sensor reads the magnetic pickup plate. If your crank angle sensor does not respond, it will need to be replaced