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New exhaust is on, but still my car drives really badly

1K views 38 replies 15 participants last post by  Makis22 
#1 ·
A while ago I put up a thread about my car and its "Lumpy Running" well, today I travelled to Dagenham to have my custom exhaust fitted, and its a really nice job, however I was really dissapointed to find out that the car still drives really badly. For those who didnt see the post before, it basically stutters and doesnt seem to have much power (except on the motorway where it will happily pull over 100mph).
Basically, the engine struggles - I thought it was down to the cat being blocked, but now with the new system it is barely any better.
Cemesis kindly popped round, and we tried different leads, but to no affect. The plugs are new, and there is some sandy brown deposits which indicates fueling is fine.
We ran the car without the air filter - still bad.
The engine has only just gone in, so oil is new as is the filter, also it has recently had a new fuel filter and damper.
I tested the fuel pump recently.
SFI box is on tightly.

The first thing we did was reset the ECU and then drive the car. It ran well for about 10 seconds until I pulled out of my road and onto the main road and then started running badly again, - could this be that the ECU is learning incorrectly once I started driving it?
We reset it twice (30 mins, the an hour) and both times it drove fine until I pulled out onto the main road then it went back to its hesitation and bad running :(

Does anyone have any ideas, as I am out of ideas and pretty depressed about it :(

PS: I then discovered the sump was cracked, so I now have 2 problems, this car is cursed.
 
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#2 ·
Have you checked all of the rubber trunking for any splits?

What about the injectors, when were they last cleaned?

What's your fuel pressure like?


Last time mine ran really poor, it was the AFM - cleaning the pins up fixed it.

HTH,

Mark
 
#3 ·
have the fuel pressure checked, and the cam timing. i presume you have no fault codes, if not you need to check all the basical mechanical stuff that wouldnt show as an ecu or sensor fault. go back to basics.

oh and p.s, dont trust the crank pulley timing marker. get a long rod down no.1 spark plug hole, and make sure its in the dwell period of TDC when the cam sprockets pass through their markers.
 
#4 ·
I have had a good look at the hoses - cant see any splits.
car is on 75k miles but the injectors havent been cleaned. Thing is it was fine then suddenly started misbehaving?

Not sure if the fuel pressure is great or not, how can I check if it is normal or not?
OK, I will have a look at the AFM contacts cheers.

0dders, it was running fine after the engine was put in by Richard - could the cam timing have changed somehow after the belt was put on?

No fault codes coming up.

thanks for the suggestions so far..
 
#14 ·
Yeah, you can check the lambda (O2 sensor) by testing the voltage between the sensor and pin10 of the ecu...
TIS says.......
Disconnect O2 sensor harness plug. Measure the voltage between O2 sensor signal lead and ground terminal 10 of control unit. It should be 0.4 to 0.5V not a quote, but that's the gen.

Alternatively, get a scanner put on it and check the readings (cross-referencing with TIS is a great help)...

A duff O2 sensor would more than likely give an ecu code 44 (Lean Exhaust)....


Oh...... coolant sensor can play havoc too (about £20 from Vx)
 
#17 ·
Definitely no fault codes stored mate??

Wouldn't the symptoms suggest an induction (air leak?) or fuel filter/pump/pressure problem??...
O2 sensor would make it run rough but not bounce around the place :confused:

I'm still quite new to this diagnostic game, so please excuse me if I'm going over standard stuff
 
#20 ·
Looking on TIS, they have a torubleshooting thingy for poor acceptance of fuel, transitional trouble which sounds like it could be in the line of the problem.....

Some of the things listed to check...
MAF
ICV
Idle position switch
Coolant temp (sensor trouble?)
Injection pulse
Spark advance
Open/closed loop
O2 sensor

I would think that most of this stuff would throw out an ecu code though... and most of it needs to be connected to a scanner to check (afaik)
 
#22 ·
thanks for all the replies. If it was the lambda sensor wouldnt the fuelling be wrong and show up on the plugs?
I will check the voltage of the sensor - cheers Evil.

Yeah, vacuum leak, AFM, lambda sensor seem to be typical culprits, - would I DEFINATELY get a fault code if the AFM was broken? - how good are these ecu codes?
 
#23 ·
Davo - totally off topic but.... where in Dagenham done yer exhaust mate??

Back to business....
Fault codes are quite good at most stuff, but some problems may not chuck out a code (like coolant sensor, I think) - but then it's down to symptoms and likely problems associated with them(which is what we're thrashing out here :D )

If it was the lambda sensor wouldnt the fuelling be wrong and show up on the plugs?
The ecu can compensate for iffy fuelling and stuff so it may not necessarily show in the plugs....
I'm still thinking MAF and coolant sensor......
 
#24 ·
Evil, the exhaust was done by some guys I already knew - Pipecraft, they build custom exhausts for American cars mainly, but did a downpipe for my Rover turbo, so I went back to them. I got a full mild steel 2.5" system and backbox for £180+VAT - bargain. Cemesis got his done there on Friday. Let me know if u want their details.

hmm, coolant sensor, I will have a look at that, and the AFM aswell. Trouble is I cant do any testing until I have a new sump on it now because it pi55ing oil - damn it all! Its going to be out of use again for another week by the looks of it. At least I am off work tomorrow so I can get the sump and gasket.
 
#25 ·
Pipecraft, they build custom exhausts for American cars mainly
I know Pipecraft (gotta remember, I'm from Barking ;) ) they refused to do me a system for my old XR4i a few years back :( but they sorted a nice bit of pipework for my Bro's old Suzuki Katana 1100....


Don't think you can test the coolant sensor.... I've just replaced the one in Kirstys' GSi (worked out just under £20 trade from Vx). MAF's are a complete mystery to me, we need to find someone to set Kirstys' one up properly (it's been messed with too much)...

Good luck mate, shame you're so far away, I'd have stuck the scanner on your car and got some (possibly useful) readings for you
 
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