'Chugging'

[jmec]

Hi, My '90 325 cab has an intermittent slight 'chugging',/'hunting', (these are the only descriptive words I can think of) when in any gear without load. I feels like the car's in the wrong gear! Any ideas please. All filters, fluids plugs etc were changed less than 3k ago. I always use Shell V power, can't find any air leaks, plugs are good even colour across all 6.
I'm thinking of getting a diagnostic tool can anyone recommend a suitable device that would work on a e36 & e46 too? Thanks!

[Grrrmachine]

No, there's no diagnostic tools you can use, especially not something built for E36/E46.

If you're absolutely sure it's not an air leak, then check your throttle position switch and your blue temp sensor (TEST, don't replace).

[jmec]

Thanks for your info' so far chaps. It's not an automatic. In all honesty I'm not 'absolutely' sure it's not an air leak; where should I consentrate my search? Has the wiki got info' on TPS & blue temp' sensor?

[Grrrmachine]

Yes, it does. Check the Intake and Fuel pages, and read the Common Problems sections there.

[jmec]

Thanks I'll try & get some time on it over the weekend.

[Brianmoooore]

This sounds like typical part load hunting, caused by a weak fuel mixture.
A set of reconditioned injectors - most important (see out traders' section), elimination of air leaks, and a check on the operation and adjustment of the throttle position switch and your hunting will be gone, plus there will be a MPG and BHP bonus.

[jmec]

I've been away working hence the late thank you Brian. I'm pretty sure it's not an air leak now; followed advice on wiki etc & I have the advantage of a boroscope kit to look for hidden cracked hoses. So it looks like a recon' set of injectors for Christmas! The car's coming off the road in Sept'; I'll live with the problem until then. Thanks everyone.

[Speedtouch]

You could try spraying some WD40 or similar around the inlet manifold gasket with the engine idling; if it briefly raises the idle speed, you have a leak.

[jmec]

Cheers. I sprayed carb cleaner around the intake system but there wasn't an increase in revs. That, a good visual & a check of the blue plug, has pretty much convinced me it's the injectors.

[AardHawk]

I would adjust the throttle butterfly to two cnut hairs and reset the tps.

[reggid]

is it like hiccuping?

[jmec]

As is the way of things, reggid, the chugging seems to have gone away. Although with the roads around here resembling a bombed runway it's difficult to diffirentiate a slight chugging to to the feedback from a crapy road surface. It was a sort of hickupping though. Thanks for the advice on adjusting the butterfly, AardHawk, I'll give it a go when I get the time.

[Brianmoooore]

Don't touch any adjustments until you have proven they need adjusting! That can only be ascertained when you know that your injectors are working properly.

[jmec]

Yeah good advice Brian thanks. On the last MOT in March they had to make an adjustment (couldn't find out quite what they adjusted) to get the emissions in!

[sweep]

running to lean?

[Brianmoooore]

An E30 in decent condition should pass it's emissions test by a mile. If the levels are more than a fraction of the limits, then there is something wrong with the engine, which won't only push you towards a test fail, but is also costing you dear in MPG and BHP.
Ideally, you should all maintain your cars so that this scenario never comes close to occurring, but if you must make an adjustment to the CO pot/bypass to get a ticket, then find out EXACTLY where it was and return it to that position afterwards, then find out what is wrong and sort it.
The trouble with most MOT testers is that they are presented with a succession of scrap from the likes of Ford, Vauxhall, or French shite with engines that are way past their best, and just don't appreciate the quality of the engineering in front of them when an E30 arrives in the bay.
The backlash in the TPS will increase after a couple of hundred of thousand of miles, and it probably will need a minor adjustment at some time to ensure it switches with the throttle just off of its stop, but apart from this (and tappets on an M20), no engine adjustments are ever required.

[AardHawk]

Don't touch any adjustments until you have proven they need adjusting! That can only be ascertained when you know that your injectors are working properly.

Yes Brian, but it is very easy to adjust and if it has no effect you can readjust it at no expense and little effort. I do understand what you are saying.

Perhaps the advice to all people who turn up here looking for advice should be that no help will be given until they can prove that the engine was in perfect running condition before the problem occurred.

There wouldn't be any fun in that however.

[Brianmoooore]

That's why rebuilt injectors follow hard on the heels of eliminating air leaks.
There seems to be a remarkable reluctance to replace the injectors on their car. This is a component that is fundamental to the correct running of the engine (no feedback loop on most E30s, remember), and one that is certain to be way out of specification after 60,000 miles or so, let alone the twice or three times that mileage of the average E30.
Adjusting the AFM bypass may get you a ticket, but it doesn't make your car perform any better. It'll still be down on power and using excessive fuel.

[jmec]

Gentlemen. Thank you for all the feedback on my post. It seems to me that making an adjustment, however easy to achieve, to a poor engine will only mask or temporarily fix the problem. You would be adjusting, not to a datum but to a fault. I can't trust the garage that made the adjustment & for this & other reasons (a simple fuel leak which they didn't fix properly was the final straw) I won't be going back there. The car has been through a number of owners the last of which sent the car to his local 'specialist'. Most of the 'specialists' work, even simple stuff, I've had to rework. And as the last owner was a self confessed useless mechanic I imagine he filled it up with supermarket petrol; cheap for a reason! I can see the general reluctance to replace the injectors is down to the cost. But that will be offset by better MPG & BHP. So my path is to hang on until I take the car off the road, end of September. The 'chugging' is an annoyance more than anything else. Replace the injectors & try to get someone who knows what they are doing (I'm sure it will be easier to get an audience with the pope!) to adjust the car back to standard. Thanks again.

[Speedtouch]

Have you tried giving it an 'Italian tune-up', i.e., a damned good thrashing?

Also check the spark plug tips - they should be a light tan colour.

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

This ensures full data transfer from the EPROM chip to the processor.

Note also that the later 0 261 200 380 ECU was reknowned for blowing diodes in the idle control circuit, so check to see which you have. It is preferable to have the 0 261 200 173 ECU, which is a direct swap.

[jmec]

Thanks for the info.' I've done all the above with exception to checking the ECU part number. I'll do that soon.