Sudden drop in power then lurch

[Sandwich]

Hi All,

I have discovered a new problem on my drive home today, where on the motorway holding a steady speed my car will suddenly slow (dropping ~3mph) for 0.5 seconds then somewhat lurch again, especially so when I'd put my foot down when it happened. It's as if someone is putting the brakes on, I tried lifting my foot and it doesn't slow as quickly as this problem. When I had the car idling afterwards, it would idle nicely at 900rpm then drop to 400-500 almost stalling before picking up again in the same manner as above.

I am wondering what is to blame, although pretty sure the slowing is caused by some engine breaking so assuming fuel injection system.

My friend suggested it could be bad spark or a vacuum leak.

It's an A20A4 in an 89 Aerodeck EXI

Thanks!

[AWH]

I would suspect the ignition control module, probably placed on the distributor on your car Otherwise possible fuel problem.

Verstuurd vanaf mijn E5823 met Tapatalk

[Sandwich]

Thanks AWH, will have a read about that.
Bit of an update, car seems to idle a little more bumpy than usual, I also got some videos (1 at idle 1 at revs) of the problem happening:
https://photos.app.goo.gl/TstqkPvHRSSPXQgQ9
Have a look, they show it quite well. They were recorded stationary in neutral, so when the wheels are turning the revs drop less.

[Sandwich]

Anyone else got any wisdom they could share?

I've since bought a new coil, distributor cap, spark plugs, plug leads & rotor. Fingers crossed its one of those!

[AWH]

Those things you just acquired are always good things to start with, part of scheduled maintenance anyway and you can dismiss those now as culprits. Would be nice if that solved the problem. Also check your battery cables for tight fit and make sure all grounds are good. Keep us posted.

Verstuurd vanaf mijn E5823 met Tapatalk

[ShiRen]

Does your tachometer jump around in the high rpms? I just had the pickup in mine go bad and at one point it did feel like this, but the unsteady tach was extremely noticeable. I replaced my TEC distributor with a Hitachi unit and the issue is gone.

[AWH]

I have had the jumpy tachometer too twice, and both times it was the ICM, Ignition Control Module, that I had to replace that solved it in my case.

Verstuurd vanaf mijn E5823 met Tapatalk

[Sandwich]

Got an update.... fit the new parts listed above, doesnt seem to have solved the problem, perhaps worse. Now, especially in low revs, car will struggle to pull and be quite jolty. Do you know where I can source an ICM in Europe? cheers!

[AWH]

I sourced them on EBay.
Possibly Rockauto too ?

Verstuurd vanaf mijn E5823 met Tapatalk

[Sandwich]

Nice, I found a few on eBay after a few pages of searching, will grab one and cross fingers. I've added another video to the link above (might need a few mins to upload), shows it after the new parts when driving, my foot is being held steady and you can see how the car lurches, all the time before the jerk it feels pretty gutless and underpowered, and the jerk itself is pretty staccato so makes me think its more spark than a vacuum issue.

[Oldblueaccord]

Before you continue to swap parts try an few free things.

1. Double check your timing since you might have moved the distributor and messed up you static timing. You set this at idle warmed up,vacuum lines plugged.

2.While driving I would pinch off the two vacuum lines that goto the distributor and see if that effects the cruise surge you are talking about. That means there is wear in the vacuum advance plates inside the distributor.

I wouldnt pull the vacuum lines off because the plastic advance is usually brittle as glass and the little male ports snap right off.

One line is for when you start the car cold and one is for regular advance when the car is warmed up. I'm never sure which is what on what car so block them both and see what you get.

[Sandwich]

Before you continue to swap parts try an few free things.

1. Double check your timing since you might have moved the distributor and messed up you static timing. You set this at idle warmed up,vacuum lines plugged.

2.While driving I would pinch off the two vacuum lines that goto the distributor and see if that effects the cruise surge you are talking about. That means there is wear in the vacuum advance plates inside the distributor.

I wouldnt pull the vacuum lines off because the plastic advance is usually brittle as glass and the little male ports snap right off.

One line is for when you start the car cold and one is for regular advance when the car is warmed up. I'm never sure which is what on what car so block them both and see what you get.

I gave it a try using zipties to pinch both lines, and seemed on the cold start to run well then removed the zip ties for comparison and it ran worse, then tried some slightly fatter zipties again and it was still worse, makes me think it could be to do with how warm the engine is not neccessarily the vacuum pinching, although its possible the second zipties couldnt get tight enough.

Checked ECU flashes, it blinks once when key turned, is that to tell you its okay (lights working)? or that the oxygen sensor is bad?

Not sure on how oxygen sensor would contribute to this. I'm sorta suspecting leaky injectors too perhaps? it can take quite a few turns to start, and sometimes won't without me putting my foot down to 'help' it, they also likely havent been changed in a while...

got the ICM, but havent fitted it yet, will try that now. - update, ICM didnt fix it!

I didnt touch timing because I dont have the tools for it, could there be a difference that means it runs well cool and is worse when warmer? atm when im putting my foot down the car takes a good while to pick up revs, I've uploaded another vid to the link above showing this at idle (when i say nowmy fott goes down and is held for the whole video), doesnt sound very nice either :/

any help appreciated

[Sandwich]

Right, gave it a few runs round the block from cold. Idles and runs well when cold, as temp gradually increases, slow and jerk gradually increases. therefore, seems to be an issue when engines warm, not sure how this would affect vacuum or spark, maybe it is the vacuum diaphragm on the distributor?

[AWH]

Sorry ICM didn't do it . Vacuum advance is worth the try as well. Also wondering if choke isn't coming off, as should when warm. Really hope you will fix it. These engines are picky, and hard to diagnose as symptoms are so much alike between components. Dud you change coil as well. Sometimes when warm they fail as well...

Verstuurd vanaf mijn E5823 met Tapatalk

[Sandwich]

Sorry ICM didn't do it . Vacuum advance is worth the try as well. Also wondering if choke isn't coming off, as should when warm. Really hope you will fix it. These engines are picky, and hard to diagnose as symptoms are so much alike between components. Dud you change coil as well. Sometimes when warm they fail as well...

I checked coil and not sure really... detailed problem on this post: https://www.3geez.com/forum/efi-tech...ml#post1221738

thanks for these suggestions, will look into them!

[Oldblueaccord]

I surely dont like that knock sound. you may want to check your oil pressure some of that sounds like a loose rod bearing.

I would still follow on up on it as a mis fire but that sound as the RPMS come down isnt a good one with no load on the engine. You can pull each plug wire ,one at a time, and try what your doing in the video and see if the motor sound changes.

[Sandwich]

I surely dont like that knock sound. you may want to check your oil pressure some of that sounds like a loose rod bearing.

I would still follow on up on it as a mis fire but that sound as the RPMS come down isnt a good one with no load on the engine. You can pull each plug wire ,one at a time, and try what your doing in the video and see if the motor sound changes.

That's an answer I didnt want to hear! I've got a blow in my exhaust so hoping its just that and the sound recorded funny, although will definitely check this up...

edit: Is this something I can pre-lim check by whipping my valve cover off and wiggling like in this video? https://www.youtube.com/watch?v=X4znxWa5Ot0

[Oldblueaccord]

Well that's the oil pan off..rod bearings are on the crank shaft.bottom of the motor. Valve cover is the top.

Wouldn't hurt to check the top and double check the timing belt lines up at TDC correctly. Then do a compression check on each cylinder.

[Sandwich]

Well that's the oil pan off..rod bearings are on the crank shaft.bottom of the motor. Valve cover is the top.

Wouldn't hurt to check the top and double check the timing belt lines up at TDC correctly. Then do a compression check on each cylinder.

right, gotcha, had a google a look at a few more vids and see what you mean. I know compression is down on cylinder 1 (and its burning oil), assumed this was just a piston ring though...
cheers.

[Sandwich]

Got a feeling its vacuum advance diapraghm, anyone know where you can get them? none on UK eBay or RockAuto it seems. Dont really wanna buy a whole new dizzy since I got all those new parts ;(

[AWH]

I got one off Ebay WorldWide last year. Lot of them too. Make sure pick the right one. Was about € 50,- iirc.

Verstuurd vanaf mijn E5823 met Tapatalk

[AWH]

Here's my order.

Verstuurd vanaf mijn E5823 met Tapatalk

[AWH]

.

Verstuurd vanaf mijn E5823 met Tapatalk

[Sandwich]

.

Verstuurd vanaf mijn E5823 met Tapatalk

Hah! was just about to ask, and you read my mind! cheers AWH

[Sandwich]

I got one off Ebay WorldWide last year. Lot of them too. Make sure pick the right one. Was about € 50,- iirc.

Verstuurd vanaf mijn E5823 met Tapatalk

The picture for that one only seems to show 1 line, but i've got 2 on my aerodeck, is it only 1 on your prelude or am I missing something?



edit: this looks more like it I think Standard Motor Products VC339 Distributor Vacuum Advance, Honda Prelude 84 85 86 87 - My Bay Car Parts