1988 320i bogging, rough idle. Need help bad!

[gasgasrob]

hi there,

Went out in the e30 after fitting coilovers (with the bonnet open raining in slightly) in the wet and the car developed a very bad bucking and stalling issue.

At first start up it idles well and smoothly, then with a light throttle it will rev (fairly smoothly) then the idle will be very erratic and lumpy but will eventually even out again.

Also, it sounds like it has a misfire upon revving to around 3000 rpm but at high revs is responsive and normal.

If I open the throttle hard from idle it will not rev at all and bogs down.

I have been over the CPS (clearance is good, metal sheath at sensor is broken but wires look ok)

I have checked for vac leaks and cannot find any anywhere.

I have unplugged the AFM while running and nothing seems affected, still wont rev hard at all.

I have just changed the dizzy cap, rotor arm and plugs so that cant be the issue.

The car smells very heavily of fuel under the bay under light throttle up to 6000rpm

I have cleaned the ICV and that seems to be working correctly.

The diaphragm on the Pressure reg seems ok under a vac test.

Sorry for the long list of information but I'm really stuck with the next step of what to do!

Any help would be much appreciated!

Thanks

[Sasquatch]

Check connection to the coil, make sure all the leads are on correctly. Also check if there are any flat spots in rev range, the afm might have a worn graphite track in some places (easy fix)

[gasgasrob]

I have checked the inside of the AFM and it LOOKS good, plenty of carbon track left from what I can see. Leads all good.

I may try bending the arm to improve the AFM though!

[Sasquatch]

Are you able to check the fuel pressure when under idle or at revs?

[Grrrmachine]

Did it all work fine before you fitted the coiloverzz? If so, you've likely disturbed an electrical connection somewhere and it'll be an easy fix.

[pacerpete]

On a positive note, at least it looks dope / gape !

[Sasquatch]

What year is the car? If it is pre-facelift you may have moved the connector to the external fuel pump or something simple like that.

[Speedtouch]

Clue to that is in the thread title -1988!

Try disconnecting the battery and leaving it for an hour to reset the ECU, reconnect, then let it idle for at least 10 minutes to enable base idle settings to be learnt, then switch off, then take it for a drive throughout the rev range.

[gasgasrob]

1988 where would the connector be for the fuel pump? I thought the pump was under the seats (lift pump anyway)

[pianist]

After you changed dizzy and plugs did you actually drove it to test? Also did you change ht leads at same time?

[gasgasrob]

i didnt change the ht leads no perhaps I should. the plugs and cap were what I thought was the problem but made no difference

[Sasquatch]

Clue to that is in the thread title -1988!

Yeah I missed that, although I have seen, all be it locally the so called 316s which is a facelift car and has an external pump

[pianist]

i didnt change the ht leads no perhaps I should. the plugs and cap were what I thought was the problem but made no difference

So you changed dizzy and plugs after the problem started?

Check ignition coil is properly connected and check there is a good earth to the engine

[gasgasrob]

coil looks ok, connections look good no corrosion. Just changed earth to sump with new strap, all good. disconnected battery and reset ecu it made no difference.


THIS IS SO ANNOYING

thanks for replies

[gasgasrob]

It WILL rev out cleanly on a very light throttle but anything more and it bogs, splutters and bucks. at first start up the idle is very smooth then after a rev it will not idle smoothly, like its hunting for fuel but it wreaks of fuel and the plugs are very wet, indicating an ignition problem?

thanks very much mate.

[Speedtouch]

Have you checked the blue temperature sensor?

http://www.e30zone.net/e30zonewiki/inde ... emp_Sensor

[gasgasrob]

would the sensor cause it to run stupidly rich? and bogging and idle fluctuation? the symptoms occur whatever temperature the engine is at

[Speedtouch]

Yes, if it or the wiring between it and the ECU is faulty - it's a common cause of over-fuelling on BMWs.

So, check the resistance at the ECU socket.

[gasgasrob]

just fitted new coil, ecu and FPR and no difference. AFM is the only thing left to change really!

[Grrrmachine]

There's no point blindly swapping parts. Test the blue temp sensor at the ECU plug, as Speedtouch says.

[gasgasrob]

the parts were quite cheap and easy to get so I thought I might aswell.

If the AFM is disconnected when the car is running nothing changes, still splutters and bogs. Surely this is a sign of a bad AFM?

[Grrrmachine]

Trouble is, changing parts means disturbing the wiring which means introducing new faults where none were previously. So it's not a question of cost, but practicality.

Your test regarding the AFM proves nothing. If it's another part that's faulty then the spluttering will persist, AFM plugged in or not.

[gasgasrob]

Changed AFM and its had no effect.

below are two videos that show what is actually happening. I believe the sound is slightly out of time with the video but you can hear it backfiring through the airbox!

http://s301.photobucket.com/user/gasgas ... 4.mp4.html

http://s301.photobucket.com/user/gasgas ... b.mp4.html

[Grrrmachine]

Test. The. Blue. Temp. Sensor.

And for the sake of the car, replace the intake boot. Your one is in shocking condition and probably isn't helping things much.

[gasgasrob]

Resistance of 176 ohms when cold

[gasgasrob]

http://i301.photobucket.com/albums/nn56 ... 79695b.jpg

reading after 5 mins of running

[Grrrmachine]

If you're testing at the ECU plug (you should) then your cold reading is far too low - it should be 3500-4000 ohms, not low hundreds. This will lead to significant lean running issues on a cold engine, including backfires. Considering the temp sensor doesn't really change after 5 mins of running, it does suggest the sensor is knackered.

[gasgasrob]

ok thankyou ggrrrmachine. I have one sitting here now. I have tried with it plugged in but in ATMOSPHERE and the problem persisted. From cold obviously I assumed the coolant temperature would be very similar to atmospheric temperature

[gasgasrob]

although I admittedly did not test the resistance after fitting new sensor to the connector. wiring issue?

[Grrrmachine]

By testing at the ECU you're seeing if a wiring problem exists. It's very common for the C191 plug (under the intake manifold) to corrode, meaning the temp signal doesn't get to the ECU, causing these sorts of problems.

If you do fit a new sensor, it's worth clearing the ECU memory by disconnecting the battery and earthing the live lead. Then with a cold engine, restart the car and let it idle for ten minutes. Switch off then restart and take it for an aggressive drive. That will help re-teach the ECU what the temp readings should be.

[gasgasrob]

I have checked that big plug and although all pins look old and rusty, they all show good continuity

[gasgasrob]

I will crack on with changing the blue sensor tomorrow, I have noticed only tonight that the fuel pump/ICV is going mental and constantly sending power to the ICV and the fuel pump is going crazy too! without the keys in the ignition but with ECU plugged in.

[Speedtouch]

Sounds like you either have a busted ignition switch, or a wiring short somewhere.

[Grrrmachine]

That sounds like your DME relay is locked, keeping the circuits constantly powered, or as Speedtouch says, there's a short in the wiring in that general area.

To confirm, see if you have 12V on pin 15 (+) of the ignition coil, even with the ignition off.

[gasgasrob]

Could it just be a faulty relay?