So I'm still having a bogging issue with my 5.3 cold. For the first mile or so in the morning I really can't give the car heavy gas, I just have to feather the throttle and let it barely accelerate.

This isn't necessarily cold outside temperature, just when the car is cold in the morning. This is particularly annoying because it makes it hard to pull out and there is a hill within the range it occurs in.

What factors into the engine management in this scenario for an HE? Should my go-to be the cold start injector? Does one of the coolant temp. sensors come into play here?

 

Your '88 won't have the cold start injectors as Jaguar eliminated them 1984-ish. They only worked while the starter was engaged anyway....so they only influenced cold starting, not cold running.

The Coolant Temp Sensor is what first comes to my mind. It's next to LH thermostat and is the primary player in fuel enrichment for cold running. You can check it with a ohm meter; I (or someone else) can give you the specs. Or....they're only $25 or so if you wanna just have a stab at it. That's not too hateful as guesses go.

Cheers
DD

 

That is also my #1 go to with that scenario.

It is not unique to Jaguar, it is a Bosch sensor.

0 280 130 026 is the last number I have from Bosch.

Add to the check list:

Fuel enrichment vac switch, usually tucked down the side of 5A inlet track. Blue/White valve with a vac hose and 2 wires.

It richens the fuel by about 15% as vac drops under acceleration. They fail and age is not on their side now.

 

Thanks, I'll check these over the weekend. I have a coolant temp sensor in the garage, but I think its probably the RH side one, which is only for the gauge as I recall.

 

It might be worth testing if the vacuum system for the ignition advance is actually working as it should. I'd want to T in a vacuum gauge right before the distributor and see what it does after a cold start.

A description of what it should do is here: VACUUM IGNITION ADVANCE / AJ6 Engineering

 

What RPM does she tick over at after being started?

 

Hi Grant

Is this the Vac Switch 'Thingy' you were talking about?

What would happen if this fails



What would happen if this Vac Switch 'Thingy' Fails?

 

Alex,

Thats the dump valve for the vac advance on Pre Marelli cars. Maybe the Marelli have them also to dump vacuam from something else, dunno.

This is the Fuel enrichment valve I am referring to.

 

Alex,

Thats the dump valve for the vac advance on Pre Marelli cars. Maybe the Marelli have them also to dump vacuam from something else, dunno.

They fail also and are a source of a small vac leak that can reek havoc.

This is the Fuel enrichment valve I am referring to.

Attachment 207064

 

OK Grant

Got it Cheers!

Is that economy Gauge (in the pic) a 'Wind Up' or did it come off your Lawn Mower?

P.S. Looks like the Marelli has also got a Dump Valve

 

The gauge is a vacuum gauge. Typically for carburettors, there is a vacuum enrichment usually around 5" Hg. If you stay out of that range the carb isn't enriching, thus the "economy" marking on the gauge.

Some EFi systems do that too, the pic you posted Orange isn't a dump valve, it's an enrichment switch - again, it's sensing manifold vacuum and telling the ECU to enrich at low vacuum, i.e. heavy throttle conditions.

The dump valve is vent vacuum to the vacuum advance capsule under heavy throttle to prevent detonation. It's a way of retarding timing under heavy load.

 

Alex,

Yes its a Vac gauge and damn near as old as me.

I use it a lot for all sorts of trouble shooting.

In this case, I am adjusting that valve to suit an engine and driver requirements. The syringe is from the local "dealer", and simulates engine vac for what I am doing.

Simple, just like me.

The mower, no got such fancy stuff, in fact it failed to cut grass recently, and failed to start, and annoyed me at the time, so I shot it, now I got a new mower.

 

Off the top of my head I don't recall, 1000-1200 cold?

 

OK, if that high, then a low tickover is not the bogging cause. So to continue the search:
When were the plugs and dizzy cap and rotor last changed?
Also, this could also be a symptom of leanness, is the fuel pressure OK?

 

new fuel reg, new fuel pump, dizzy cap has been changed since it started and the plugs are probably 10k miles old.

 

OK, back on subject.

Does the car still have the vac delay for USA emissions??.

I am not familiar with that system,. but have read over the years that it is complicated, and messy.

Try a temp vac hose from the inner spigot of the underside of the RH throttle body, duly plugging any ports/hoses removed, and try that at cold.

That is the only vac advance plumbing that Greg and I run. NO complicated delay valves etc.

Depending on the system I mentioned above, some trimming of the timing may be needed with this plumbing.

Also, timing is subjective at best. Lots of things have changed since this car was new. I set all mine at 10 BTDC, and then trim the timing in the advance by "drive timing", and thats worked for a very long time.

10K on those plugs is still OK. I usually get 40K kms from the HE's, and sometimes notice hissy stuff earlier than that. Without starting another fuel flame comment, we do not have Ethanol fuel here, and I run our highest RON in them all (98). They are not happy campers on the lower (91 or 95), and I stopped looking at why 20 years ag, 12.5:1 needs some decent "go juice".

 

I'll check into the vacuum stuff tomorrow, got caught up in schoolwork and the XJ6 today.

I run top-tier premium all of the time, but I have had full tanks of regular in it without any knocking, keeping in mind this is 11.5:1, which is still pretty high. Can't imagine its a fuel quality issue, its definitely feels like a cold fuel:air issue.

 

SS,
Something just posted to Doug by Grant reminds me. IS the TPS setting bang on? If it is too low at tickover it could cause your problem, as the throttles open but the ECU does not get the signal above the tickover setting until a bit late.

 

Greg,

Good on ya.

That is why that spacer is required when setting the TPS, to get the electrics up and running before the discs open.

Also, the balance of the opening of the 2 discs, MAINLY off idle, is very critical. So if one disc is lagging the other, the imbalance could cause "bogging".

 

Spacer?

That's not ringing any bells. What am I missing?

Cheers
DD