325i Sport Hesitating when Running

[Corrado1441]

Hi I have a 1989 BMW E30 325is with The 2.7 Engine conversion done.
Just got The car so not sure of its quirks.
Car starts 100% but idles like its off a cylinder, and when driving it hesitates Very badly.
After driving for a while it gets better but not 100%, does not seem to pull like it should, but up around 5000 rpm it seems ok???
Tried unplugging MAF and Engine runs rougher, definately better with MAF plugged in.
There is a blow out in The exhaust.
Also on downshift it backfires, not sure of thats to do with The stainless system or The Engine conversion.

Any Help appreciated.

Also The 3 relays by The MAF in The black box, what is The white one, its a Siemans, part number 12.63-1729004. I discovered a previous owner had fitted a switch across 2 of The wires and hidden it behind The glovebox

Cheers.

[e301988325i]

Right. . . two problems at the very least;

poor idle + backfiring on the overrun is the TPS not registering idle, if it were functionning properly then the fuel cutoff would be activated in these conditions and no backfire would be possible. When you're on the overrun the econometer needle should swing all the way up to the left practically out of view, I'm sure it won't be doing this. (Another albeit unlikely possibility is the FPR is leaking through the vacuum hose into the inlet manifold but this is unlikely and I've not heard of this happening). To reset the TPS you'll have to remove the throttle body, clean inside whilst you're there and don't adjust the throttle/buttterfly stop screw!

If there are three relays fitted, is a lambda sensor fitted? If not the lambda heater relay should not be fitted, the ECU uses the fitment of this relay to determine that a lambda is fitted or not and a default value should be used. An OEM lambda relay should be blue, although the orange fuel pump relay next to it is the exact same part and is fully interchangeable. On my M20 the lambda relay is the rearmost of the three, although these positions can be moved around if the car has been fiddled with. If you pull either the DME relay or fuel pump relay the car will definitely not start so at the very least a process of elimination can be conducted.

[Corrado1441]

Ok thanks
The 3 relays are 1 white and 2 yellow.
Going to try new plugs car was lying parked up for 2-3 months.