Engine stuttering when changing gear?

mike1978

Hi,

I`ve got my engine tidy and running - its an EJ20 non turbo.

It pulls away really well and idles without any probs. But when i come to change gear, the engine really stutters and almost dies, then i struggle to get the van moving again. I`m not sure what the problem is.

I`ve checked for exhaust leaks and can`t see any. There was a couple of leaks round the inlet manifold but i`ve fixed those now and i still get the same sympons.

Has anyone any idea of what the problem could be? I made the exhaust myself - could that be the problem? Or could it be something else?

Here`s a pic of the exhaust, its pretty loud - too loud for me! -

Cheers,
Mike

mike1978 · Posted: Sun Apr 27, 2008 1:14 pm Post subject:

To further explain the probelm, you`ll be driving with a high rpm, i drop the clutch, shift gear, let the clutch back out and put the throttle down again and the engine completely stutters and nearly dies.

i guess it could be lack of fuel? this is the fuel pump that i bought -

http://cgi.ebay.co.uk/NEW-V8-EFI-Type-Bosch-Fuel-Pump-ROVER-JAG-TVR-MGB-etc_W0QQitemZ110231672552QQihZ001QQcategoryZ10414QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

should this be sufficient? i`m also running a plastic filter (which possible should be a metal one?) before the pump.

Once you`ve changed gear and got over the stuttering, you can drive without the engine faltering - its only when you drop the clutch, change then give it more revs to pull forward again that the problem occurs.

Any input is apreciated. Thanks, Mike

rjes · Posted: Sun Apr 27, 2008 2:44 pm Post subject:

Hello Mike,
Does this happen only at high speed, or maybe at all speeds, but worse at high speed? It sounds very similar (although not exactly the same, in my experience) to one of the symptoms of not having a vehicle speed sensor on an engine which needs one.
In particular, if you stop at a junction after driving at a high, fairly constant speed (dual carriageway, motorway, etc), does it stall as soon as the revs, drop, as if you've turned the ignition off, then restart with no problems at all?
If so then I suspect you need a speed sensor. Your engine (MY98?) is of the age where it's very difficult to know for sure whether a speed sensor is needed or not without trying it. As you had the optional front extension harness, it's all pre-wired for a speed sensor. Two screws and one plug, and it's fitted. As your symptoms are possibly slightly different, I'll send you a speed sensor to try if you like. If it solves the problem, pay for it, and send me as much detail as possible about the symptoms you had with no sensor, which I'll include on the rjes.com for everyone elses reference. If not, send it back.

PS - I'm not surprised that exhaust is loud! There can't be much silencing in it at all.
_________________
Regards,

Richard,

R J Engineered Solutions
Quality Subaru Powered VW Components
www.rjes.com

mike1978 · Posted: Sun Apr 27, 2008 7:51 pm Post subject:

hi richard,

it does seem to happen at all speeds although i didn`t drive above 30mph - i drove it for about a mile or 2 and this happens on every gear change. I managed to get up to 3rd gear but then i kept it there and at about 30mph as i didn`t want to risk changing up to 4th in case the engine spluttered and i had traffic behind me!

i`ll give you a ring tomorrow regarding the speed sensor. Another sympton that i forgot to mention was that if you put your foot down it sometimes hesitates and then comes to life. if it wasn`t all controlled by computer i`d say the carb mixture was too lean maybe but obviously i can`t change that.

And yes - i think i`ll have to get a larger silencer - its more embarrassing than anything!

Thanks,
Mike

rjes · Posted: Sun Apr 27, 2008 9:07 pm Post subject:

It sounds a lot more severe than any speed sensor symptoms I have heard of before. No error codes, I assume?

However, a possibly likely other cause could be much closer to your 'if it wasn't computer controlled' option. As you lost the throttle position sensor setting the other day, unless you are absolutely certain that it's now set back exactly where it should be, the ECU could be supplying the right amount of fuel according to the sensors, but the throttle valve being out could be allowing too little / to much air through.
_________________
Regards,

Richard,

R J Engineered Solutions
Quality Subaru Powered VW Components
www.rjes.com

mike1978 · Posted: Sun Apr 27, 2008 9:36 pm Post subject:

yes i thought about the throttle position sensor - it could be that it wasn`t in exactly the same position. i tried to search for info on how to set the position exactly using voltage values from the wires but could`nt find much info.

richbaker78 · Teacher of Padawans Joined: 31 Jan 2006 Posts: 1298

have you got enough fuel in it this time Laugh Out Loud

Joking aside it does sound like a fuel restriction - is your pump receiveing enough power? have you any restrictions in your fuel line? fuel filter installed correctly? Fuel filter new or old and clogged?

i assume there are no back fires or popping noises?

what air filter are you using also? make sure there are no restrictions to the inlet or airleaks.

once youve covered the basics i would start looking at the sensors particularly the MAF.

mike1978 · Posted: Mon Apr 28, 2008 9:50 am Post subject:

lol - yes there is enough fuel now!

there are some popping sounds - i just thought that this might be large exhaust sliencer that i`ve used. I have checked for inlet and exhaust leaks though and there doesn`t appear to be any now.

this is the air filter i`m using -

http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=360029999428

i don`t think there are any restrictions in the fuel line - there is a new fuel filter (plastic though) installed before the fuel pump - i`ll check that it s the correct way round tonight. the pump is receiving enough power i`m pretty sure - it makes enough noise althuogh i have rubber mounted it!

i drove it at high revs in 3rd gear at about 35mph for about half a mile and it didn`t stutter or anything - just when dropping the revs off to change gear it has the problem when applying the throttle again.

i`m also gogin to check that the throttle position sensor is in the correct position aswell using my multimeter as i`ve had this off for cleaning.

richbaker78 · Teacher of Padawans Joined: 31 Jan 2006 Posts: 1298

hmm if the popping is under load or on holding a constant RPM then its most likely indicating a lean mix - so something controlling the fuel supply/ mixture (lmabda, MAF, etc) or an air leak.

If the popping is on decelleration then it is probably jsut some small holes / leaks in the exhasut and unlikelty to be related to your problems.

The filter looks like its an oiled type?although it doesnt mention it in the blurb....ive no first hand experience of this but there is certainly a lot of chat about using oiled elements on subarus on the scooby forums. The Mafs dont like it. If it is oiled then do a search on scoobynet about this - i think you can clean the MAF with carb cleaner - then run it without the filter to see what happens.

just to be clear....you say you ran it at high revs is that becasue its the only way you can achieve enough power or is it fine on power you just cant get it past that point?...in other words did the engine have the normal / expected amount of power or was it down on power across the range? If its labouring and struggling to make power thrrougout you are runing lean probably as a result of an airleak or sensor prob however if its strong on power but then hits a wall then you have some sort of restriction - either physical (to inlet or fuel) or poss. sensor related.

probably oversimplified that as theres a numebr of reasons that might not be the case....but just some thoughts really.

mike1978 · Posted: Mon Apr 28, 2008 10:34 am Post subject:

the popping is on decceleration (sp!?) so i put that down to small holes maybe in some of the welds.

i get can get good power and pull away well. i held it a high revs in 3rd only because i was on a 60mph road with traffic behind and i thought travelling at 30mph was probably better than stuttering to a halt when trying to change up to 4th.

thats something to try regarding the airfilter - i `ll have a search on scooby forums.

doppelganger · Posted: Mon Apr 28, 2008 3:16 pm Post subject:

mike1978 · Posted: Mon Apr 28, 2008 7:23 pm Post subject:

well, i think i may have found the problem - another `schoolboy` error!!

after fiddling about with the throttle position sensor which turned out was set dead right after testing the voltage, i noticed the vacuum pipe for the fuel pressure regulator wasn`t connected to the inlet manifold -DOH!!!!

Laugh Out Loud

had a drive round the block and it changed gear with no probs Grin

just got to get a decent silencer now!