I am trying to help a mate out here.

Anyway he is trying to tune his 305 HSR but it is becoming a headache.

At first he had a problem with surging and backfiring. I ended up burning a chip for him with the $6E mask and revamped the spark advance table. Disabled the EGR. It ran really good, all his issues were gone, except for the fact it was running a bit too rich at idle.

He did not have a scan tool at the time.

Now all of a sudden the car is running rough again. No matter what chip you put in they all work the same. I also supplied him with a bone stock $6E chip and it makes no changes if he puts it in. But that chip worked well, but down on power compared to the revamped sprk advance table which is understandable.

The idle is down low at about 500 and stalls after a while.

Someone wired up his fans and they took +12v from the ignition coil. Could this have something to do with it?

Maybe a bad ECM?
VAC leaks might be the culprut?


Basically no matter what chip he puts in the car now it just runs the same. Very hard starting basiclaly need to floor the pedal for it to start. Yet 1 week ago after he had the fuel pressure regulator replaced it started like a dream.

THere was some work on there was some work on the car done this week but nothing that should affect the performance. Other then the fans.

When he disconnects the MAF it runs even worse.

No codes are thrown. I think I might have to re burn a chip for him and set the injector constant up a bit to lower the fuel.

Any other tests or tricks to look for?

I told him about the fuel pump voltage to check that.

After reading all the MAF problems people have, it really does seem that the MAP system is more user friendly.

Also out of curiosity would a bone stock engine only with the HSR intake make the car run very rich?

He says that the car is pretty much stock and the only mod is the HSR. Is it possible that with a stock chip, the HSR would make his car so rich that it hardly wants to idle?

His problem to start with was that is was surging and backfiring. And not idling well at all too. It was suriging in idle. All off a sudden it has gone the other way around.

I should also mention, there was a time when the car ran like dream at cold temp then when it warmed up it got worse. Now it is just running bad all the time. And like I said no codes.

 

MAP vs MAF is pointless discussion when there are other problems.

if the car ran fine other than slightly rich idle and then suddenly went to running like crap, then changing things in the tune isn't going to fix it (or at best work around the problem), the real problem of course is that something broke or went bad,

check the new fuel pressure regulator to make sure it's still working ok (proper pressure both with vacuum applied and not), broken/cracked vacuum lines, heck it sounds like it's worth a total goings-over (full tune up + inspection), pull the plugs and read them (clogged/stuck open injectors?), do diagnostics and found out what broke/went bad.

Edit, I see you made another post (should have replied in this one) about having the prom inserted one pin off and that the problems started then. the obvious thing to do now is to reburn the same code to a new chip, and if that doesn't solve the problem, swap the ECM for a known good one. they are durable and rarely fail, but if the bad running is directly tracable to a mis-inserted chip...well then likely it's the chip or ecm.

 

Thanks for your reply. The problem was solved. It was a fried chip on the ECM. Replaced ECM and back to normal except for some tuning issues.