HELP - Engine Running Rough After Wash


I’m presently stuck at my office, and not sure what to check on Superblue (my '94 4.0 coupe).

Earlier tonight, I decided to finally try to wash off all that engine oil that had accumulated in the recent past due to the backend of the valve cover gasket being blown, prior to my r/ring same a couple of weeks ago. I followed the directions on the Gunk cleaner can by letting her cool a bit at the car wash, then spraying everything down in the compartment, letting that soak for about 10 minutes +, then rinsing everything off with the wand, using the fine (weak) spray final segment of the wash cycle only. After waiting a few minutes, I started her up and everything seemed fine. As directed (and from my previous experience with my XJ40s) I made sure to drive her around for over 1/2 hour with the engine fully warmed up before shutting her off, to make sure everything dried out in there (there was a little pooling of water around 4 or 5 of the plug boots, but since the boots were tight in the plug holes, nothing leaked in, apparently). Again, everything was fine, and I parked her at my office.

A few hours later, I go to start Superblue up and she’s missing badly, like she’s only firing on 3 or 4 cylinders, and will hardly idle. :astonished: I checked everything visually under the hood, and everything there appears dry. Just last week I had installed new plugs and new plugs wires, including the coil hood, so I can’t imagine water getting in anywhere there and fouling things up I haven’t had a chance yet to replace the dist cap and rotor, so could water have gotten in there somehow, although everything seems tight with that?

Give it a few more hours and will whatever is fouled clear up, or do I need to call a tow truck now and expect another trip to the shop this week? :angry:

(Ian) #2

Water and car electrics just don’t mix , should avoid the 2 getting together at all cost !
that’s too late now .
Spray all the electrics with WD40 , and pray :pray:

(DavetheLimey) #3

Remove your distributor cap and look inside. I’ll bet you will have water in there. Dry everything with paper towels, including the rotor. Then drive home.

(phillip keeter) #4

If you have access to a compressor, use the high pressure on “everything” in the engine bay getting in all the nooks and crannies. Great way to dry that what you can not see.

(motorcarman) #5

My recommendation on washing engines is DON’T!!!

Here is a TSB we got regarding Vehicle washing.

600-02 Pressure Washing.pdf (26.8 KB)

Jaguar does NOT recommend under hood cleaning as a routine practice, nor the practice of applying by spray, detailing products to the engine, engine bay, under hood pipes and hoses, and other components to obtain a ‘showroom’ finish. If a high finish is desired, hand detailing is recommended.

A hand spray bottle of something like ‘Simple-Green’ and a damp rag would probably be fine.

I sorted out many ‘no-start’ problems when customers washed their engines and Jaguar DOES NOT cover this in new car warranty. (customer pay for self inflicted faults).
Customers got angry when Jaguar Warranty would not pay for this repair.

I usually disconnected many electrical plugs and used WD40 (Water Displacement 40) and compressed air to get all the connections dry again.

Back when the Generator and Distributor were the only ‘electrics’ on the engine you could get away with engine washing.


(scrimbo) #6

Probably you will find inside the rotor cap a fine fog of moisture. …clean it…then don’t do the water thing anymore…also there is a spray dryer for ign wires…you can get moisture in the dist cap towers where the wires plug in.

(Robin O'Connor) #7

Regardless of the plug boots being new I would also check for water in the plugs, especially as its a misfire on a few plugs.


Spot on, Robin. :+1: I looked things over very carefully after my post, and what happened is that, despite the apparently tight fit of the new spark plug boots (the round seals) to the spark plug holes, water had gotten past them and pretty much flooded plugs #1, 4 and 5 (I was right about it hitting on only 3 or so cylinders!). Took a lot of blasting with my air duster and brake cleaner spray (along with dabbing down into the holes with a shop rag) to drive enough of the water out of the holes to get her firing O.K. again. :relieved: First thing I did was drive her to a local car wash where I sucked the rest of the water out (as I did with the oil that had dripped into them before the plug and wire r/r) and then used the hot air wand on same for good measure. Bottom line is don’t count on the tight fit of those rubber seals to prevent the ingress of water (fluids?) into those spark plug wells!

Bob, interesting service bulletin, btw. When I was trying to figure things out, I checked out a 15-minute+ “real time” video on YouTube which is done by an “engine bay detailing pro” here in the Dallas area in which he shows the proper way to do the job on a customer’s car. Pretty much he started out like me, with something akin to Gunk + brushing, followed by low pressure water rinse (he used distilled, though) He then used a leaf blower to thoroughly blow off/out any remaining water (VERY IMPORTANT). He then said, if desired, you can use a product for shining up the plastic bits which is made just for that purpose on engine bays (I think he recommended Macguiars). This same person has a 10-minute video where he expounds at length about NOT using any silicone-based products, such as Armor-All, in that area. He warns that many cheapo detailing people will skip the water part of the cleaning process, assuring the concerned customer that water could harm things in there but the products he uses supposedly won’t. The unscrupulous detailer then pretty much just applies and wipes off the product to all visible parts of the bay. However, those products leave a film that (1) the customer can smell from even inside the car, when things heat up in there and (2) even worse, instead of draining directly off the bay, the product can work its way inside electrical connectors and other electrics where it can really reek havoc over the weeks ahead. He said many of his calls have been from customers to have him remove the offending product that was applied by other detailers. :anguished:

(Michael Garcia) #9

maybe wd’ing
areas one would
not be exposed
to h2o
to washing…

douse with detergent
wait a sec
pressure wash
with a shield,
like l usually do…

wait over night
before turning it overt

(Andrew Waugh) #10

Also, don’t presume that water ingress problems will manifest themselves shortly after the water ingress.

About a month ago my DD was due for it’s MOT. As always, I power washed it, then drove back to the shop, and while it was still warm, used compressed air to thoroughly blow dry the engine bay.

I failed the MOT as the rear main seal was leaking, so I did that and replaced the clutch while I was in there.

The day after everything was back together (and running perfectly) it started showing an EGR fault (which is an MOT fail). My initial thought was “I must have damaged/disconnected the sensor while I had the exhaust was hanging down (multiple expletives deleted)”, but when I put the diagnostic machine on it it indicated that the intake air temperature sensor was throwing faults.

I pulled the connector and sure enough… there was water inside. This despite the rubber boot and seal being intact. A quick brush with a glassfiber pen and a washout with contact cleaner returned everything to normal and I passed my MOT.

This fault didn’t manifest itself for nearly 2 weeks.

(Carl Hutchins, Jr. ) #11

Aye and nay, and lessons learned…

A long time ago, I was an advocate of the Warm engine, add gunk. let stay. Wash off with plenty of water. Hot is best. At times, I masked off the air filter and distributor. Others not. At ties, they ran lousy til the engine heat cooked off the water that was where it should not be. And, at times, the distributor cap had to be removed and the internals wiped or blown dry.

Gone process. No more water in the engine bay…

Just wipe and wipe and wipe!!!

Yeah, wehen I got my really nice 85 Ford F150 4x4 it had been detailed to the “max”. Some goop rubbed on everything, in and out. A light oil, I think!! It shone. It took a lot to get it off !!

I got to talk to the detail guy., He agreed, he did not like it, but his car sales clients insisted!!! Ugh…

Armorall, aye and nay. I leaned the hard way. Not on a vinyl bench seat!!! M back side slid on every move…