First Gear Lurching / Surging
 

When I bought my ti, one of the reasons I got the deal that I did was because the car was lurching in 1st gear with moderate to aggressive acceleration. He thought it was the clutch going out, but when I discovered the broken diff mount I assumed that I had found the problem. Nope.

When I take off, the car will sometimes buck and lurch almost like the fuel is getting cut off repeatedly. It doesn't do it every time, it varies in severity and only does it in first gear. Seems more prone to do it when cold and when turning left. It'll sometimes do it when going straight, it hasn't done it yet when turning right. (I haven't driven it enough to know for sure.) Keep your foot out of it and it won't do it at all. Acceleration in 2nd-5th is smooth and strong.

The symptoms don't seem to point to the clutch as the previous owner suspected because when it's real bad it'll actually chirp the rear tires with every lurch. I'm wondering if I've got bad motor mounts and the engine is moving around too much.

Thoughts?

Well, it's plausible. Maybe the broken diff mount caused excessive movement, which caused an engine mount to fail. Or vice versa. Only one way to know for sure.

I plan on getting under it this weekend to check the engine and trans mounts as well as the rubber coupling in the driveshaft (giudo?), u joints and center bearing.

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Salguod;

Guido is a greasy haired, loud-mouthed, New Jersey hipster (or gangster). Guibo is the driveline joint you are referencing... :biggrin:

It seems like the broken diff mount was a symptom, not the issue. Yes, check your motor mounts as well as your trans mounts.

How's your idle, especially after warming up the engine for a few? This issue doesn't "smell" like a clutch, because that would happen after all shifts. I suspect something else, based on what you have posted so far...

Thanks for the guido / guibo clarification. :-D

Idle is perfect, from first start to warmed up.

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When coasting in neutral at 15 mph, the idle should be 1000rpm. This insures smooth driveability at low speeds. Idle drops to 750rpm at stop. Check to make sure the driveline is tight. Guibo (flex rubber coupling can crack or disintegrate), half shafts, center bearing, u-joints, transmission mounts, engine mounts.

I'm gonna get crazy nitpicky here and admonish everyone that it is actually 'Giubo' (pronounced: 'Jew-boh'), and named so after its inventor: GIUnti BOschi.

When you rev the engine while stopped, does it rev smoothly through the RPM range?

I thought that was the spelling, but managed to spell it wrong each time. :tongue:

Idle is as you described, although it doesn't quite rise to 1,000 RPM when moving more like 900. It revs just fine, although I haven't rev'ed it to redline in neutral.

A couple of other notes:

First, there's a clack clack sound up front when turning the steering wheel when stopped or at very low speeds like in a parking lot. I assume this is bad strut bearings and not likely related to the surging.

Second, there is an occasional quiet, dull thud from the rear after I stop. Sometimes immediately after stop, sometimes delayed, sometimes not at all.

Considering the mileage, what I have into it (about $700 so far) and how well it drives aside from this, I'm starting to consider doing the engine & trans mounts, the giubo, the center bearing and the u-joints. They are all original (I got most of the records from new and work with the PO who had it 14 years) and likely very worn anyway. Even if that's $500 in parts, I'll still only have $1,200 into it.

At any rate, I'm not deciding anything until I get under it and look around this weekend.

Didn't have as much time as I thought today, but I did get the front end up in the air and take a quick look. I discovered two things, first the driver's side lower ball joint is loose and second the frame mount on the passenger side for the stabilizer is rusted away. Neither seems like a likely cause.

The giubo and trans mounts look like new, but I couldn't spin the drive shaft to see the whole thing. I hope to get the rear in the air tomorrow to get a better look. It looks like you can't see the center bearing without removing the exhaust, is that right?

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Well, unfortunately, no smoking gun.

Rear suspension is tight all around, nothing loose.

Spun the drive shaft and the giubo looked new all around.

I couldn't see the center bushing without pulling the exhaust & heat shields, so I have no idea how it looks.

After I pulled it off the stands, I opened the hoood and blocked the front tire (parking brake is not working). I then let the clutch out in first, rev'ing the engine to put a load on it while I watched the engine through the hood. No excessive engine movement telling me that the engine mounts are OK. I'm somewhat tempter to take the hood off and watch the engine when it bucks to be sure.

While under the car I did notice two things that I'm not sure how normal they are:

1. If I grabbed the transmission and pushed side to side, there was a decent amount of movement, maybe 1/4" - 3/8" each way. The mounts looked good, but were pretty soft.
2. If I grabbed the half shafts amd pushed side to side, each moved a fair bit as well, the driver's side a bit more than the passenger. Probably 3/8" and 1/4" respectively. No torn boots or axial play.
3. Ahead of the transmission cross member was a lighter duty bracket with two torn rubber mounts on it. Obviously, whatever had been there was gone. Some kind of splash sheild maybe?

I'm not sure what to think at this point. I guess I'm leaning toward u-joints and maybe the center bearing, but that's just a guess. I may have to concede and take it to a shop for a diagnosis.

More info (for anyone still paying attention :smile:). The soft thunk from the rear happens when I put the car in gear. So, car stopped, foot brake applied, clutch in, slide into 1st - clunk. Doesn't happen every time, but most times.

I'm really leaning towards a bad u-joint, which means a new drive shaft (& center bearing & probably giubo). I guess I might just have to drop the exhaust to check it. Sigh.

Does it clunk as soon as you release the clutch after putting it in 1st or the moment it goes into 1st gear only before releasing the clutch?

The TI uses a dual mass flywheel. The dual mass could be separating causing the thug.

Thunk is when it goes into gear before I release the clutch. And the Thunk is definitely coming from the rear. It's not very loud.

The thunk is rear gear lash and is normal on high mileage rear ends. If you get under the car with it in neutral you should be able to turn the drive-shaft a little both ways and feel the gear lash. I would look at engine mounts and transmission mounts for your issue. It sounds like something is moving around when you are in first gear causing the feeling of a lag...

John S

I would agree about the engine mounts, except I'm not seeing excessive engine movement when I hold the car and rev the engine in 1st gear. If the engine is shifting, it ought to do so then as well.

Oh, and it's not a lag, it's hard, tire chirping, lurching. I should try to get it on video.

I should have the car up this weekend to change the control arms, I'll check the lash then.

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