Engine cutting out, low revs & low load

[Ryan23]

Hey Guys -
Little background, three weeks ago I received a new set of HT leads & plugs. The old leads were showing their age and did not have the metal extensions. When I pulled plug 8 off, the boot literally fell apart in my hands. It was cooked. However, the car ran "great" before that. Only had the very minor shunting @ low rpm/high gear which I just attributed to an idiosyncrasy of TVR ownership .

I only briefly fired the car up after the leads to verify everything was kosher. I still did not have the metal extensions as they were enroute from the UK along with some other goodies. A couple days later though, the meltdown @ Fukushima power plant happened and my ship had to relocate. So here we are three weeks later, I'm back home, and spent my birthday busting my knuckles on the Griff.

I fitted the ACT silicon inlet (quick & easy) along with the plug extensions. I verified everything was making good contact and set out for a drive. First thing I noticed is a big stumble at low revs. Most notable from a standing start. If I'm *really* careful on the gas pedal I can prevent it from bucking. It will cut out, briefly, then come back. I can drive through it but I look like...umm...(scratching head for something British)... a hooligan?

I've noticed it will occasionally stumble @ 2000 RPM but not consistently. What does bring it out though is a low manifold vacuum condition. My drive is pretty steep and if I lug the car in first gear up the drive it will buck, bark the tires, buck, ETC. On the flipside, when I boot the car on the street, she will pull cleanly to 5500 without a hitch in second/third/fourth.

I've checked all the leads and the extensions 3-4 times now. I really don't think it's the plug wires though. I wouldn't think it would completely fall on it's face like that. Idle is rock solid @ 900 RPM. Free revving the engine in neutral doesn't cause it to sputter.

So I'm making a list of possibilities. I've got a new fuel filter, haven't fitted it just yet. Car has only done 14,500 km since new and was obviously pampered. I'll change the filter but, in my mind anyway, it's not likely. O2 sensors? Maybe? Wouldn't the car have a garbage idle though? Same for the MAF? TPS... need to check that. Cap & rotor both looked good. Bible mentioned something about the tank vent potentially being blocked. Popped the gas cap on and off, no change. Has anyone had something similar crop up?

Thanks in advance!

Ryan

[Colin RedGriff]

Possibly an air leak on the inlet side?

[Bodmin]

Colin RedGriff said:

Possibly an air leak on the inlet side?

Ryan,the easiest way to check for an air leak is to spray WD40 or equivalent around the inlet manifold joints with the engine running.....if the engine revs rise you have a leak & you should be able to pin point it.

The TPS should be between 0.33-0.35V at idle.

Bodders

[Ryan23]

Well, you know what they say... "When something isn't acting right, look at the last thing you changed".

• I checked the TPS, .36V @ rest, varied proportionally with the throttle opening.
• Changed the fuel filter, what a PITA!!! If someone knows the chap who brainstormed the fuel filter location (with *just* enough fuel hose slack), please kick him in the shins for me.

Went for a drive, would still intermittently cutout as you leaned into the gas.

• Bypassed the vacuum advance, because it was something I could do on the fly, no change.
• Then I remembered I had my old plug wires in the trunk. Swapped the coil wire out... BINGO!

Looking at it in the daylight, I can see why. The OEM coil pack was swapped to an NGK coilpack for some reason or another in the past. It used this tacky looking red lead with a glass capsule where you can visually see the spark activity. The new HT lead set I ordered came recommended from the LR community. 8mm silicon leads from "Spark Transfer International" (STI). They are decent and have held up to the heat thus far. Not bad for £35 posted. Well, the STI coil wire has the same end for both the dizzy and coil (like most coil wires I've seen). This particular coil uses a different style connector for the coil side though.

Now, on the old coil lead, the car is back running like a top. So, in celebration, I took a trip out to my favorite (semi-nearby) road in the Hakone area near Mt Fuji. Car behaved and didn't bite me! I'm a technical driver but I will admit a bit of trepidation on our first "official" outing together. As the car clawed at the tarmac and swallowed up the esses with that wonderful V8 grunt, I couldn't help but have the occasional thought run through my head, "She will kill you at her earliest opportunity..." But we made it back safe and sound without even so much of a scare. I find the car very predictable thus far. Here's a Google Earth shot of the road where I can usually be found in one of the cars. It's a nice road that turns into a *great* road after 10pm on a weeknight. While the headlights are absolute garbage, the foglamps + headlamps are AMAZING!



P.S. Decatted the car last weekend, now it sounds like a proper Griff!

Ryan

[TV8]

Glad you sorted the car and Arab looking road. I bet it doesn't have safety cameras either!

[Ryan23]

TV8 said:

Glad you sorted the car and Arab looking road. I bet it doesn't have safety cameras either!

No speed cameras, no police, no speed bumps and best of all... no traffic!