m52 obd1 power loss

[e-dirtym52]

I have a 91 m52 converted to obd1 with a m50tu harness. I'm using a trm chip but I'm still running into a few problems. so basically I can get on the throttle about a quarter to halfway and it seems to cruise ok. but once the throttle is pushed past that it jus completely loses power and goes nowhere. I can stay halfway on the throttle and raise the rpm and it doesnt limit anywhere. I ended up putting in a spare ecu with the stock chip and it actually didn't really cut the power when getting on the gas it just ran like shit. so I'm calling trm tomorrow to figure something out with the tune but I wanted to know what everyone thought before hand or invade fixing the tune doesn't take it away. I changed the fuel filter and was going to test the pressure on the fuel pump after I call trm. so anyones input really helps! thanks guys

[e-dirtym52]

well I ended up calling trm and they said that they're pretty sure it's not their chip. he said typically if the car starts then the tune is working properly.

[CarsSuck]

Step 1: check TPS
Step2 : check MAF

does your check engine light work? Do you have a code reader?

[e-dirtym52]

cel works but no code reader. I unplugged the Maf and it runs even worse so I know my Maf works. I unplugged and cleaned the sensor on the tps. I've looked for vacuum leaks and cant find any. the guy said to check all my injectors and my fuel pump.

[nrubenstein]

Step one: fix your diagnostic port.
Step two: borrow a fuel pressure gauge and test that. Unexplained bogging under throttle could easily be the fuel pump taking a shit, or a clogged fuel filter.

[e-dirtym52]

I replaced the fuel filter and I was going to check fuel pump tonight. it just stumps me because with a stock tune 413 I can go full throttle and it won't completely cut power. is that just because the stock tune is for 17 lb injectors so it's not pushing enough gas to make it cut power?

[nrubenstein]

I replaced the fuel filter and I was going to check fuel pump tonight. it just stumps me because with a stock tune 413 I can go full throttle and it won't completely cut power. is that just because the stock tune is for 17 lb injectors so it's not pushing enough gas to make it cut power?

It should run fine on the M50 tune. More aggressive tuning can highlight problems. If it runs like shit, there is still an external problem.

Check fuel pressure, then start working your way through the sensors. And fix your damned diagnostic port.

[e-dirtym52]

ok. I'll check fuel pump pressure tonight. I heard some stuff about wiring in a vss. but everything I read on that people say they need it because they limit at 3500. that still wouldn't be a problem since I dont limit will it?

[nrubenstein]

ok. I'll check fuel pump pressure tonight. I heard some stuff about wiring in a vss. but everything I read on that people say they need it because they limit at 3500. that still wouldn't be a problem since I dont limit will it?

You should have the VSS wired up, but it won't make the car run constantly like crap. It will impact performance and the rev limit (although not necessarily to 3500 - when I swapped clusters and had VSS issues, I ran into the limiter at 6500).

[e-dirtym52]

alright well I'll give this fuel pump test a go and see how that ends up. thanks for the info!

[King Mufasa]

How is your idle doing? Do you have a picture of your crank sensor setup?

Iam assuming you are using the updated crank sensor with adapter harness for the m52.

[e-dirtym52]

idle is iffy. sometimes great sometimes a little rough. at times when the engine is cold it will stall and other times it's super smooth